The Science of Evidence

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1Forensic Science and Criminalistics

Associated Press

Learning Objectives After reading this chapter, you should be able to do the following:

▪ Define forensic science and how it contributes to a case, as well as explain the CSI Effect and the scientific method.

▪ Summarize the history of forensic science and contributors to the field.

▪ List and describe some forensic science specialties.

▪ Identify the elements of a forensic investigation, how physical evidence can be produced, and forensic analysis.

▪ Describe the work and work product of a forensic scientist.

▪ Describe the U.S. court system, and the key rulings on physical evidence admissibility through expert testimony.

▪ List and discuss major issues in forensic science today.

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10Blood and Other Biological Fluids

Doug Mills/Associated Press

Learning Outcomes After reading this chapter, you should be able to

▪ Recognize and describe different types of bloodstain patterns and how they occur.

▪ Discuss preliminary and confirmatory tests for biological fluids and how this evidence is collected and preserved.

▪ Explain the different types of sexual assault cases and the role of backlogs and the SANE program.

▪ Describe how sexual assault evidence is collected and preserved and how alcohol and drugs can factor into assaults.

Section 10.1Blood Patterns

Introduction In this chapter we will discuss two important topics: blood and other biological fluids as evi- dence for lab testing. Blood is the human lifeline and is often shed in violent crimes. It is left behind either by a victim, a suspect, or both. Blood patterns are an important category of pattern evidence, as the information they convey by their formations can help reconstruct the events of the crime. Blood and other biological fluids, such as semen or saliva, play an important role as evidence in crimes such as sexual assault and can help include or exclude suspects and determine innocence or guilt.

The analysis of blood and body fluids discussed in this chapter is called preliminary because it occurs before DNA analysis. The specimens must first undergo identification testing to deter- mine what they are and whether they are human. If they are, and if it is determined that the particular specimen needs DNA analysis, it will be sent along for that procedure.

In large, busy labs, there is usually a division of labor between the analysts who conduct the preliminary testing (described in this chapter) and those who conduct the DNA analysis (described in the next chapter).

10.1 Blood Patterns Chapters 8 and 9 discussed fingerprints, handwriting, and firearms and tool mark identifica- tion, which are all categories of patterns for individualization. In other words, under the best circumstances, a comparison can associate a questioned specimen with a specific, individual origin. As you may recall, there are also patterns for identification (classification) and for reconstruction. Blood patterns are an example of a pattern for reconstruction.

Forensic scientists can specialize in bloodstain pattern interpretation, and those who do often belong to specific professional organizations, such as the International Association of Blood- stain Pattern Analysts. Sometimes bloodstain pattern interpretation experts also have exper- tise in forensic biology or in deoxyribonucleic acid (DNA) analysis. The dried blood in blood- stain patterns must go through DNA analysis in addition to pattern interpretation because it is important to know whose blood made the pattern, so it is helpful for specialists to have knowledge of both areas.

Blood patterns may be called dried blood patterns, bloodstain patterns, blood spatter patterns, and sometimes even blood splatter. Despite the various terms, they refer to the same thing: the patterns of dried blood made from blood leaving the body and hitting a target surface.

When blood leaves the body, it can ooze or drip out through a wound or pump out through an artery. Once outside the body, it may soak onto skin or clothing or drip onto another sur- face. It might be further spattered by some force, be transferred to another surface, or run or drip because of gravity. All these events lead to the formation of patterns. As it goes through these events, blood obeys simple physical laws like any other liquid. Because these physical laws are consistent and predictable, investigators and analysts can formulate interpretations of the patterns that are formed. These patterns provide information about the events that caused them and thus may help reconstruct violent events, for which it can be difficult to obtain accurate eyewitness testimony.

Section 10.1Blood Patterns

Velocity and Angle of Impact One way to classify blood patterns is with reference to the velocity of the droplets that form those patterns. There are low-velocity, medium-velocity, and high-velocity bloodstain patterns.

Low-velocity blood patterns are formed by the force of gravity alone. All objects fall toward the ground unless they are held in place or some countervailing force prevents them from fall- ing. Blood droplets are no exception. Low-velocity patterns are dripping patterns. Someone could be walking with a small wound that is dripping blood or carrying a body that is dripping blood; the blood then hits the ground or other surfaces. These bloodstains are circles, and they may have small, linear-like projections that radiate out from the circle like the rays of the sun. These are called satellites, and an example of one is shown in Figure 10.1. The presence of satellites in a pattern depends on a couple of factors. One is the target surface. They are vis- ible only when the surface is hard. If it is irregular (like a rough-hewn sidewalk) or absorbent (like cotton cloth), you won’t be able to see them. If blood hits an absorbent surface, it spreads into the substratum and obliterates any satellites. If the surface is irregular, the satellites will not form a recognizable pattern.

Figure 10.1: Blood droplet with satellites

Blood that lands on a hard surface from a high enough distance can result in a bloodstain with satellites, as shown in this figure. How do you think the presence of satellites could help with reconstructing the events that occurred at a scene?

Adapted from “How Bloodstain Pattern Analysis Works,” by S. Freeman, 2008, Retrieved from http://science.howstuffworks.com/ bloodstain-pattern-analysis3.htm.

The other important factor for low-velocity patterns is distance of fall. If blood drips within inches of a hard surface, satellites will not appear. However, if the blood drop source moves upward, increasing the distance of fall, it will reach a height at which the bloodstain will show satellites. This is because of the droplet’s velocity as it travels through space. As the source moves upward, the velocity of flight increases, and the droplet hits the surface harder. This knowledge can sometimes help estimate the distance the droplet fell. There is a maximum limit for the velocity of flight, however. Laws of physics state that at some point, the drop- let reaches terminal velocity, meaning that it will not fall any faster, no matter how high the

Section 10.1Blood Patterns

source. Therefore, a droplet falling from around 6 feet won’t produce a pattern much different from one falling from the top of the Empire State Building (discounting air and wind effects). The Empire State Building droplet will be traveling at the same velocity as the 6-foot droplet when it reaches its target surface.

Another parameter that can change the pattern is movement of the source. It is the speed of the movement that affects the pattern. If a source is moving slowly, the droplets will be round. Such circular droplets do not indicate the direction in which the source may have been mov- ing. But sometimes, if the blood source is moving faster, the pattern can change to give an indication of the direction of movement. The satellites will not be evenly distributed around the circle. Also, the droplets may be slightly elliptical—not truly circular—suggesting that they struck the surface at an angle slightly different than 90°. The side of the circle with the satellites suggests that this was the direc- tion of the source. This type of interpreta- tion cannot be deduced from one or two bloodstain droplets. The whole pattern— all the droplet stains—must be analyzed, since some stains will provide more infor- mation than others.

Medium-velocity blood patterns are the result of a force greater than gravity being applied to the droplets. The result is that the blood droplets break up into smaller ones and appear in circular and elliptical shapes, indicating that the droplets hit the target at different angles.

Medium-velocity blood patterns are often seen in blunt-force assault cases, such as when someone is beaten with a blunt weapon such as a bat or a brick. The weapon breaks the skin on the first blow, and blood pours out onto the skin and pools. When the weapon strikes again, the pooled blood is spattered by the force, causing the pattern. A pattern like this is also seen when someone stomps through pooled blood. Forces greater than gravity are always involved in the production of these patterns.

High-velocity blood patterns result from greater force than that causing medium- velocity patterns. These patterns are gen- erally seen as a result of a gunshot or an explosion. If someone is shot in an uncovered part of the body, such as the head, arm, or chest, high-velocity blood spatter will occur from the wound entry toward the shooter (back spatter) and from the wound exit (forward spatter) if the bullet exits. High-velocity blood droplets are very small; some are the size of aerosol mist

Photo courtesy of R. E. Gaensslen A medium-velocity blood pattern can be seen in a blunt-force assault case. The blood droplets in this pattern consist of circular and elliptical shapes.

Section 10.1Blood Patterns

droplets, and they do not travel very far. If a gun is close to its target, there may be high-velocity back spatter on the gun or on the hand or clothing of the shooter. The presence of forward spatter from the exit wound means a target surface was quite close to the shooting victim. Otherwise, the droplets would fall to the floor or ground before forming a recognizable pat- tern on a surface.

The other important factor to be con- sidered with spattered blood droplets is angle of impact (incidence). The droplet in Figure 10.1 hit the target surface per- pendicular (at an angle of 90°) to it. As a result, it is round (circular). But a droplet hitting a surface at any other angle will form an ellipse-shaped stain. You can see the effect of angles on blood droplets in Figure 10.2.

Figure 10.2: Blood droplets at different angles of impact

Blood droplets at different angles of impact. Impact angles are expressed with reference to an imaginary plane perpendicular to the surface, not with reference to the surface itself.

Adapted from “How Bloodstain Pattern Analysis Works,” by S. Freeman, 2008, Retrieved from http://science.howstuffworks.com/ bloodstain-pattern-analysis3.htm.

The angle of impact is measured with respect to an imaginary plane lying perpendicular to the surface. Thus, when a blood droplet hits a surface at 90°, the angle of impact is 0°. The degree of ellipticity (noncircularity) of the blood droplet stain is mathematically related to the angle of incidence. Using precise measurements of a droplet and some trigonometry, it is

Sociologas/iStock/Thinkstock High-velocity blood patterns can be caused by a gunshot. The blood droplets are small and do not travel far from the entry and exit wound of the victim.

0° 50° 70° 80°10° 20° 30°

Section 10.1Blood Patterns

spurts of blood near the injured person is observed. The spurts are produced as the heart beats, forcing blood through the arteries under pressure and forcing blood out of the body through the wound onto the nearest target surface. A person cannot live long with a severed artery. Blood is pumped out of the body in large quantities, blood pressure drops quickly, shock ensues, and the person dies.

Movements (Trails) Movements, or trails, are dripping, low- velocity patterns. If the source of the blood is moving quickly enough, the droplets have associated satellites that may indi- cate direction. This type of pattern is typi- cally formed if someone is walking while bleeding or carrying a bleeding victim.

Contact Transfer If a bloody object comes into contact with a target surface, the pattern of that object is transferred to the target surface in blood, which is known as contact trans- fer. Suppose a person wearing pants with a distinct weave pattern kneels in a blood pool. The blood will transfer to the knee of the pants, and the weave pattern might transfer to the surface containing the blood if it is nonabsorbent (such as a lino- leum floor). If a bloody baseball bat is placed on a white sheet on a bed, the pat- tern of the portion of the bat that made contact with the sheet will be transferred in blood. Sometimes the patterns are not that distinctive and the object that caused the transfer is not obvious. The object may have been removed from the immediate area or from the scene, making it more dif- ficult to figure out what caused the trans- fer pattern in the first place.

Running A running pattern occurs when blood is deposited on a vertical surface in suffi- cient volume that gravity causes it to run downward.Photo courtesy of R. E. Gaensslen

Arterial spurts such as this one happens when an artery is severed and blood exits the wound via the pumping action of the heart.

Photo courtesy of R. E. Gaensslen This trail of blood shows that the source of the blood was moving while the blood dripped off. Based on the satellites, can you determine in which the direction the source of blood was moving?

Photo courtesy of R. E. Gaensslen When a bloody object touches a surface, contact transfers are created. At times, the transfer can be an identifiable shape. In this case the object that transferred on this piece of clothing might not be as distinct.

Photo courtesy of R. E. Gaensslen Blood that is on a surface and trickles downward creates a running pattern.

possible to calculate the angle of incidence for any droplet. These calculations can be quite useful in reconstructing the approximate point of origin of a medium-velocity blood pattern. If a selected, representative set of droplets is measured and the incidence angles calculated, straight line markers like string can be placed into the pattern representing the angles. These straight line markers will converge near a point. They don’t converge exactly at one point, because there is uncertainty in the measurements and in the placement of the string strands. But the point of approximate convergence is close to the blood source for that pattern, assum- ing the pattern resulted from one source.

Types of Blood Patterns In addition to low-, medium-, and high- velocity patterns, a number of other types of blood patterns can be identified. Each of these will be discussed in the following sections.

Cast-Off Cast-off, or arc, patterns result when a bloody object is swung in an arc-like fashion and blood droplets are thrust off the object by force onto a target surface. Imagine someone swinging a baseball bat over his or her head and back down again in the manner of forming an arc on the ceiling. If the bat is bloody, the blood droplets on the ceiling will form a cast- off pattern. The pattern is a series of blood droplet stains deposited at differ- ent angles along the arc. If there is enough blood on the object, two arcs will be observed, one from the swinging move- ment in each direction. The swinging motion could be vertical, horizontal, or along some other intermediate plane.

Arterial Spurts Arterial spurts occur when an artery is cut and a characteristic pattern of large

Think About It

Blood patterns form in varying ways, depending on the velocity and angle at which they fall. How would you start trying to reconstruct a crime scene that involves a number of dif- ferent blood drop patterns, some of which overlay each other?

Photo courtesy of R. E. Gaensslen Cast-off is usually created when blood comes off an object, such as a bloody bat. This image shows two arcs, showing that the bloody object moved in two different directions.

Section 10.1Blood Patterns

Running A running pattern occurs when blood is deposited on a vertical surface in suffi- cient volume that gravity causes it to run downward.Photo courtesy of R. E. Gaensslen

Arterial spurts such as this one happens when an artery is severed and blood exits the wound via the pumping action of the heart.

Photo courtesy of R. E. Gaensslen Blood that is on a surface and trickles downward creates a running pattern.

Section 10.1Blood Patterns

Wipes and Swipes If an object moves through a preexisting wet bloodstain, the stain pattern is termed a wipe. The object can be anything, includ- ing a hand or arm. A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another sur- face, showing characteristics that indicate relative motion between the two surfaces, is called a swipe. When hair or a finely strung broom with many fiber strands is bloody and is dragged across a nonabsor- bent surface, the result is a swipe pattern because it has distinct lines in the stain pattern caused by the individual strands of the broom or hair. This type of pattern is often observed when someone with a lot of hair receives a head wound that has gotten the hair bloody and is dragged across a room by the feet.

Secondary Spatter Secondary spatter patterns result from blood dripping into a preexisting pool of blood. If blood is dripping from a source onto a nonabsorbent surface, and the source does not move, a secondary spatter pattern forms around the blood pool, which will also form on other nearby tar- get surfaces, such as a wall. If it is a medium-velocity pattern, then the force causing it is the droplets hitting the blood pool and spattering the pooled blood. If there is a vertical surface nearby, and the angles of incidence of the droplets are studied, it can be determined that the blood droplets were splashing upward from the pool.

Photo courtesy of R. E. Gaensslen Blood found at crime scenes appears in various patterns, including wipe bloodstains. How do you think this type of bloodstain pattern could help determine what happened at a crime scene?

Photo courtesy of R. E. Gaensslen When blood drips onto a preexisting pool of blood, it causes secondary spatter. The blood dripping on the already formed pool of blood can cause droplets to splash upward.

Section 10.1Blood Patterns

Bloody Impressions When bloody impressions such as fingerprints, footprints, or footwear or tire impressions are formed, special handling and processing may be required to analyze the primary pattern and the blood. Investigators will want to know whose fingerprint it is—a fingerprint iden- tification issue—as well as whose blood it might be—a DNA profiling issue. This topic was discussed in Chapters 8 and 9.

Blood Pattern Interpretation A number of factors must be considered when interpreting blood patterns at crime scenes or in connection with criminal events. It is important to understand that a blood pattern can help investigators reconstruct one small aspect of a complex set of events. We may know that a certain event that gave rise to the blood pattern occurred at some point, but it is difficult to know its timing in relation to other events. Therefore, blood patterns aid in only partial recon- structions of events. For instance, there might be a running pattern on a wall. This means that blood in sufficient quantity ran downward on the wall at some point during the crime. What does this mean for the case? How can it help investigators understand the overall events at the scene? Depending on the case, the scene, and the circumstances, the pattern might or might not be helpful.

The target surface can drastically change the appearance of a stain pattern. If the blood is quickly absorbed by the receiving surface, for instance, characteristic patterns may not form at all. Common examples of absorbent surfaces are cloth and dirt. In that case, the blood pat- tern may not help determine what type of event occurred.

Another factor that is important in blood pattern interpretation is the need to run experi- ments. Investigators and forensic scientists can try to experimentally reproduce the situation at the scene and the events that may have caused the pattern. If the same or similar pattern occurs, they can be confident that the proposed explanation for the pattern is reasonable. But they cannot know if their version of the event actually occurred. The experiment shows that the explanation is within the realm of scientific reality, but it does not prove what happened. Experiments are not always necessary. But the more an expert plans to say about a pattern, the more likely it is that he or she will need to try to reproduce the pattern experimentally.

In order to use blood patterns to understand the case events, it is necessary to know the source of the blood. This information comes from DNA profiling. Sometimes there is only one person who is bleeding (known as a bleeder) at a scene, and all patterns are derived from that blood. But if there is the possibility of more than one blood source, that information is crucial to arriving at a correct interpretation of the scene events.

Think About It

How do you think secondary spatter patterns could be helpful in reconstructing a crime scene? What information about the movements of individuals in the scene could you get from such a pattern?

Section 10.1Blood Patterns

The following situation outlines a homicide case and presents a few pictures of evidence from the scene. After reading through the case and looking at the pictures, see if you think the sus- pect’s account of the events makes sense.

Case Illustration: An Illustrative Homicide Case Involving Blood Patterns

A man and his wife were living separately but had not yet divorced. One day the police received a call from the husband frantically asking for help, saying that his wife had been attacked and badly injured in her apartment and that they should get there immediately. Police and paramedics responded.

The wife was lying on the kitchen floor bleeding profusely from a stab wound to the chest. She had other knife wounds on her body. There was blood in the living room as well, but not as much as in the kitchen. Paramedics quickly treated the victim and took her to a hos- pital, where she died from her wounds. The medical examiner noted that the fatal wound was a stab wound to the chest through her heart at a slightly upward angle. Two nearly identical knives were at the scene, one on the living room sofa and another on the kitchen floor. They were serrated-edge kitchen knives, and both had blood on them.

After the paramedics removed the wounded victim, the police took pictures, examined the scene, and interviewed the husband. He had bloodstains all over his clothing, as shown on the manikin in the following images. The police later seized his clothing as evidence.

Photo courtesy of R. E. Gaensslen Overall view of blood- stained clothing on a manikin.

Photo courtesy of R. E. Gaensslen A close-up view, left side.

Photo courtesy of R. E. Gaensslen The back of the jacket.

(continued on next page)

Section 10.1Blood Patterns

Case Illustration: An Illustrative Homicide Case Involving Blood Patterns (continued)

The husband told the police that he had been at his own apartment when his estranged wife called him, very upset, and said that someone was trying to break in, so he should come immediately. When he arrived at her apartment, the door was locked and he no longer had a key, so he broke a front window and climbed through. A front window was, indeed, broken, and most of the shattered glass was inside the apartment, indicating that the window had been broken from the outside. The husband said he found his wife stabbed and bleeding and that he had cradled her in his arms trying to comfort and help her, which is how the blood got onto his clothing. Right after that, he said he called the police.

All blood samples were analyzed and found to match the victim, not the estranged hus- band. Sometimes if a person has a victim’s blood on his clothing, it provides evidence against him. But in this case, the husband gave an explanation for the blood on his clothing.

Reflect On It To have a better look at the bloodstains, their distribution, and their patterns, examiners placed the husband’s clothing on a store manikin and took photographs. Looking at the bloodstain patterns on his clothing and considering what you have learned about blood- stain patterns, are the patterns consistent with his story? If you don’t think they are, why not? And what do you think might have happened here that would be consistent with the blood pattern evidence?

Photo courtesy of R. E. Gaensslen A close-up of the left pant leg.

Photo courtesy of R. E. Gaensslen A close-up of the left pant leg cuff.

Photo courtesy of R. E. Gaensslen The pant legs.

Section 10.2Preliminary Analysis of Biological Fluids

10.2 Preliminary Analysis of Biological Fluids It is common to have two categories of tests for substances and materials in forensic labo- ratories: preliminary (or presumptive) and confirmatory. Drug chemists, toxicologists, and forensic biologists use both types of tests.

DNA profiling is quite complicated and is generally completed by specialists in the laboratory. Often it is not the same analysts who run both preliminary examinations and DNA testing, so there is a division of labor in the lab. Some analysts complete the preliminary testing, while others complete the DNA testing.

For many years the work done by biological evidence analysts was called forensic serology. The same analysts completed the preliminary testing as well as genetic testing. In the late 1990s, when DNA profiling became the only genetic testing done in forensic labs, there was a question of what to call preliminary testing. There is some agreement now that it is called forensic biology. This term is not perfect, because there are other types of examinations that are both biological and forensic, such as the analysis of botanical material as trace evidence, or human toxicology.

Before the different types of preliminary and confirmatory tests are discussed in more detail, it is important to first go over how to properly collect and preserve biological evidence.

Collection and Preservation of Biological Evidence Collection, packaging, and preservation are important parts of handling any evidence, as seen in previous chapters. Biological evidence requires some handling and preservation steps that are different from nonbiological evidence. The main reason for the difference is that biologi- cal evidence, by its nature, can undergo decay and degradation, and many things can affect its integrity, such as sunlight, bacterial action, or contamination by materials from the environment.

It is also important to understand that blood and body fluids can constitute bio- logical hazards, or biohazards, because they can be infected with pathogenic organisms or viruses. Major potential threats are hepatitis, herpes, and the human immunodeficiency virus (HIV). There are recommended universal pre- cautions in place for all health care work- ers, emergency responders, and others (including crime scene investigators and forensic scientists) designed to protect them from potential infections. The pri- mary precaution is the use of protective gloves. These may be latex, but because

some people have latex allergies, they can instead be nitrile. In the laboratory, negative pres- sure hoods, which draw any loose materials into a vacuum system and out of the building, and sometimes face masks, are routinely in use. Forensic scientists, crime scene personnel, police officers, and anyone who handles or comes into contact with dead bodies must be aware of the potential hazards and the precautions.

There are very few reported cases of crime scene or forensic personnel contracting an infec- tion from handling evidence. Taking the appropriate precautions appears to be highly effec- tive in preventing any problems. The major threats are viruses, which are transmitted through blood or body fluids by means such as transfusions of infected blood or sexual contact with an infected person. There is theoretically a small chance of transmission by other means, such as breathing blood “dust” from the handling of an item with a dried bloodstain. However, there have not been any reported cases of transmission by such means.

Collection Techniques In Chapter 2.2 crime scene processing procedures were discussed in detail. All the proce- dures covered would be used at any crime scene. Here we focus in more detail on collecting blood and other body fluid evidence. Something to remember about blood pattern evidence is that the “collection” of a blood pattern usually consists of recording it through photography, sketching, and/or video. Blood patterns are often found on walls, ceilings, and big, heavy fur- niture. It is not practical or necessary to destroy a structure to collect a blood pattern when documentation techniques are sufficient. Samples of the dried blood within the patterns may be collected and preserved using the following techniques. The blood pattern can be helpful in reconstructing events, but it is necessary to know whose blood made the pattern. That is the reason for taking the samples. Not all dried blood or body fluids that will be collected from a scene is part of a pattern.

The techniques that are used most often for collecting blood and body fluid stains are

1. collecting the intact item bearing the stain; 2. cutting the stained material out (from substrata, or the material on which the stain

is deposited); and 3. scraping dried stain residue onto a clean container surface.

Collecting the intact item bearing the stain is always the best method. This way laboratory staff can figure out how to handle the stain and the evidence and can obtain appropriate comparison specimens from them. As previously noted, however, it is not always possible. Cutting may be necessary if the substratum material is too cumbersome to collect, such as the upholstery from a sofa or a large carpet. One might cut out a piece of Sheetrock from a plaster wall that had a bloodstain on it too. Scraping is the most difficult method, because it is hard to control and collect the solids produced from the scraping. First, an investigator needs to use a scrupulously clean scraping tool. Some investigators recommend disposable tools to avoid any possible contamination of one specimen by another, called cross contamination. Scraping may have to be done with surfaces like a cinder block wall, or something similar that cannot be removed.

Cultura Limited/Cultura Limited/Superstock As with anyone who works with blood, forensic scientists must take precautions to protect themselves. Do you think these preventive measures are enough, or should there be more?

Section 10.2Preliminary Analysis of Biological Fluids

The techniques that are used most often for collecting blood and body fluid stains are

1. collecting the intact item bearing the stain; 2. cutting the stained material out (from substrata, or the material on which the stain

is deposited); and 3. scraping dried stain residue onto a clean container surface.

Section 10.2Preliminary Analysis of Biological Fluids

Controls Controls must be collected as well. The most important of these will be specimens from known persons. They are called knowns, exemplars, or reference specimens. They will also be used for the DNA typing that comes later, to determine whose blood is in the bloodstain. Controls, as you may recall from Chapter 1, are specimens of known origin. Until recently, knowns from people consisted of blood. Blood would be drawn from a person’s vein. Now it is adequate to rub a cotton swab on the inside surfaces of a person’s cheeks. This is called buccal swabbing, and it collects plenty of cells for DNA typing. The process does not require a lot of pressure, and it does not hurt the subject. If a person is dead, the medical examiner will collect the known specimen, generally blood. If blood cannot be collected, a specimen of tissue will work. Even a specimen of bone is worth collecting if no other tissue is available.

Comparison Specimens In the tests we will be discussing for blood or body fluids from stains, an unstained specimen of the substratum must be tested in parallel with the stain. This practice ensures that a posi- tive test from the stain comes from the stain substances and not from the substratum. For some time, such a specimen was called a substratum control, or cloth control if the stain was on cloth. This terminology may still be in use, but it isn’t really correct. Controls must be of known origin to be true controls, and because an unstained area of substratum from a biologi- cal stain is not a known, it cannot be a control. This specimen is instead called a comparison specimen. Investigators must be aware of the need for this specimen and be certain that it is collected. If a specimen has been scraped off a surface, for example, the investigator should scrape a bit of unstained surface to serve as the comparison specimen and label it appropri- ately. If a stain was cut away from some material, a nearby unstained piece must also be cut. If the entire bloodstained object is submitted, the lab can get the comparison specimen from the object.

Packaging and Preservation The primary rule for blood and physiological fluid evidence stains is to ensure that the stains are completely dry before the evidence is packaged. In environments of high humidity, com- plete drying may not be possible, and the evidence must be dried in an air-conditioned place.

Think About It

You are the lead investigator in a serious assault case. The events in this case happened in a very expensive imported vehicle that has custom leather seats. There are quite a few bloodstains on these seats. These bloodstains (and accompanying comparison specimens) need to be collected. You could document the bloodstains and then cut out the specimens. You could remove the entire seat assembly and submit it to the lab, where an analyst will have to cut out some stains. This vehicle belongs to the victim’s mother. She raises the issue of who will compensate her for destroying the seats in her vehicle. How would you handle this situation?

Section 10.2Preliminary Analysis of Biological Fluids

Sometimes investigators may have a crime scene van that will work for this purpose. Other- wise, the evidence has to be put into containers but not sealed until it has been allowed to dry in an air-conditioned environment—generally at a police facility. Another big factor is not packaging this type of evidence in airtight containers (like ziplock plastic bags). Airtight con- tainers and moisture promote bacterial growth, and bacteria can destroy the evidence. Paper containers that can “breathe” are used for this type of evidence. The evidence can be placed into a druggist fold made from laboratory weighing paper, for example. Then this package can be placed into another paper container that can be sealed. With big items, like a mattress pad, one might need a roll of butcher paper to contain the item.

Sometimes investigators find liquid blood or body fluids at a scene. In such a case, they can either allow the liquids to dry to a stain or use special techniques for collecting the liquids. Investigators should talk to laboratory personnel for guidance on how best to collect and preserve liquid specimens from scenes. For example, liquid specimens could be collected into small glass vials, but it is important that the vial and the device used for the collection be clean, and preferably sterile. Another approach is swabbing up the liquid with a sterile gauze pad, then allowing the specimen to dry completely before packaging and sealing. This method ensures that all of the specimen is collected.

To help preserve blood and body fluid stain evidence, it is generally stored in a refrigerator or in a freezer. The evidence should be completely dry beforehand. The lab uses freezers for specimens of this type of evidence because sometimes the lab keeps these specimens for long periods of time. For shorter term storage, a refrigerator works well. Because there can sometimes be a delay between the collection and packaging of evidence and submission of the evidence to the lab (for example, because the lab is closed), some police agencies have refrigerators in their evidence storage facilities.

Evidence Cataloguing in the Lab The biological fluid evidence that comes into the laboratory must be catalogued and exam- ined to locate blood and body fluid stains and then to decide which ones to analyze further. Because laboratories have high caseloads, it is wise at the initial stages to analyze the evi- dence in terms of what the case requires, so as to take the most efficient approach to the detailed analysis required of any blood or body fluid stain.

Analysts must keep detailed records of the evidence, recording the location of any stains found on objects, clothing, and so on. Unique identifying numbers must be assigned to any subspec- imens or cuttings to track them through the analysis. Consider a shirt with four bloodstains. The shirt will have an identifying number made by the investigator who collected it as part of the case submission. For example, it could be called “#4 shirt.” The lab will generally keep this label. The analyst must record the position of the four bloodstains on the shirt through a photo or sketch. The bloodstains must be cut out to be analyzed further, making it essential that the original locations of each stain be recorded. An analyst might call the stains “4-1, 4-2,” and so forth.

Once the relevant evidence for analysis has been selected and properly labeled, it undergoes a series of tests to identify the type of fluid present in the stain. Is it blood? Is it human blood? Is it semen? Is it saliva? If it turns out to be human blood or a body fluid, it will be sent to DNA profiling to determine if it can be associated with anyone involved in the case.

Section 10.2Preliminary Analysis of Biological Fluids

The following section discusses the testing that is completed before DNA profiling. DNA pro- filing will be detailed in Chapter 11.

Preliminary (Presumptive) and Confirmatory Tests Preliminary tests are screening tests. They should always register positive results in the pres- ence of the substance for which they are testing, but they can also sometimes register false positives. A true positive means the test registered because the substance tested is actually present. A false positive means the test registered, but the substance tested for is not actu- ally present. This is a shortcoming of the test. These tests are usually quite sensitive and fast. Questioned specimens that do not result in a positive preliminary test are usually not exam- ined further, because this result shows that there is nothing there to further examine. When preliminary tests are positive, specimens are further tested using confirmatory tests.

Confirmatory tests are certain tests that verify (or fail to confirm) the results of the prelimi- nary tests. They give positive results only when their target substance or compound is pres- ent. In the following body fluid stain discussion, we will see that confirmatory tests may not always be available. Under those circumstances, the laboratory must report that a positive presumptive (or indicative) test was observed, but it cannot report that the target material or substance is present.

Blood Tests Blood is sometimes called a liquid tissue. It consists of two main types of cells: red and white. The red cells contain hemoglobin, the principal protein of blood; it is the molecule that trans- ports oxygen to our tissues from our lungs. The white cells are involved in immunity, or pro- tecting us from diseases. They can attack infectious agents directly, and they are also respon- sible for making antibodies against infectious agents. Blood also contains cell-like structures called platelets, which are involved in blood clotting. The liquid or watery portion of blood is called plasma. From a forensic testing point of view, the red cells are important because hemoglobin is a protein unique to blood, and tests for hemoglobin are tests for blood. The white cells are important because they contain all the DNA in blood. Red cells do not have nuclei, and the DNA is located in the nucleus. So there is no DNA in red cells.

There are preliminary (presumptive) and confirmatory tests for blood. Note that this does not mean human blood. For now, it relates to blood in general.

The main preliminary tests for blood are color tests that have been used for more than a century. The most common are orthotolidine, phenolphthalein (also called Kastle-Meyer), and leucomalachite green. By “color test” we mean that in a positive test, the chemicals will change color. These tests are based on the same chemical principle, but they differ in the color that represents a positive result. The tests are based on the fact that the hemoglobin in blood will act as a catalyst, speeding up a chemical reaction that would otherwise be slow. In living cells, many proteins, called enzymes, are catalysts. Hemoglobin is the protein that carries oxygen around in blood, from the lungs to the cells. It is not an enzyme but acts like one in these tests. All blood has hemoglobin. These tests are set up so that a color change, or a fluorescence under ultraviolet light, is observed in a positive test. However, these tests are destructive in the sense that once swabbed up, tested specimen cannot be used for any further testing.

Section 10.2Preliminary Analysis of Biological Fluids

Another presumptive blood test is called the luminol test. Luminol is a chemical compound that, under certain conditions in the presence of hemoglobin (in blood), will give off light. The scientific term for this is chemiluminescence. Sometimes people involved in violent criminal activities try to clean up afterward, making it more difficult to see bloodstains. Luminol can be useful in these situations. It is usually sprayed onto surfaces that might be bloodstained, after which the surface must be observed in absolute darkness. Luminol will light up any blood present by its chemiluminescence, showing investigators where to collect the bloodstains. Spraying luminol onto a bloodstain does not interfere with subse- quent DNA profiling of that bloodstain.

There is an ongoing effort to develop more sensitive and reliable methods of blood detection. One area of current inquiry is hyperspectral imaging, which might be able to detect latent blood stains in com- plex scenes (Yang, Messinger, Mathew, & Dube, 2016). Additional research is being done to evaluate presumptive tests that may be able to detect blood on clothes that have been washed repeatedly (Mush- taq, Rasool, & Firiyal, 2016).

There are several confirmatory tests for blood. One such test of historical inter- est is the Takayama test, named after its original proposer. This is a crystal test, in which dried blood subjected to a certain treatment forms recognizable crystals

Pool/Pool/Getty Images News/Getty Images Luminol makes it difficult for criminals who clean up their crime scene to hide evidence. Do you think it is more effective as a presumptive test than color tests?

Think About It

You’re a crime scene investigator trained to perform presumptive color tests for the pres- ence of blood. A small speck of red substance—possibly blood—catches your eye. Using a Q-tip end moistened with distilled water, you carefully swab up the speck and perform a presumptive color test on it. The test is positive. The blank control run on the other end of the Q-tip is negative. Months later, in court, the question of whether the speck was actually blood becomes an issue. As the investigator, you must testify regarding your actions and the results of the test.

What can be said about the specimen as a result of the presumptive blood test? Could you say that it was blood? That it might be blood? That it is probably blood? Do you think the test should have been done? Or should you have collected the specimen and brought it to the lab, where more analysis would have been possible? Under what circumstances do you think investigators should perform presumptive blood tests at scenes? Should testing be a prerequisite for collecting a specimen?

Section 10.2Preliminary Analysis of Biological Fluids

that can be viewed under a microscope. A positive Takayama test indicated that blood was definitely present. The problem was that the test frequently failed even when blood was pres- ent (false negative).

Newer confirmatory tests for blood are immunological or immunochromatographic. The term immunological refers to antigens and antibodies. Antigens are molecules that the human immune system perceives as foreign and thus invasive. If a virus or disease-causing bacterium invades the body, the body will try to fight off the infection by producing antibodies against the invasive agent to neutralize it. Scientists can also make antibodies to almost any protein by injecting the protein into an animal under certain conditions. The animal makes antibod- ies against the injected protein, and the scientist can then collect those antibodies and use them in tests. In immunological tests, the created animal antibodies are made against human hemoglobin, which can then be used to show that human hemoglobin is present. If human hemoglobin is present, human blood must be present. This is a case in which the test not only confirms the presence of blood but also shows that the blood is human. There are several dif- ferent ways of setting up antigen–antibody tests. In one of them, the antibody’s binding to the antigen will cause the complex to precipitate out visibly in a gel medium.

An immunochromatographic test cassette is shown in Figure 10.3. Immuno refers to the anti- bodies used in the test cassette, and chromatographic refers to the fact that the test liquid migrates along a membrane within the cassette during the test.

Figure 10.3: An immunochromatographic test for human hemoglobin

An immunochromatographic test cassette such as this one is a fast and easy way to check if human blood is present.

From “H. pylori Antigen Rapid Test Kit,” by Epitope Diagnostics, 2017, Retrieved from http://www.epitopediagnostics.com/ kt113/. Used by permission of Epitope Diagnostics, Inc.

These test cassettes are manufactured in such a way that the human hemoglobin, if present, will be captured by an anti-human-hemoglobin antibody, causing a red line to appear at one

Control

Negative

Test Control

Positive

Test

Control

Invalid

Test

Section 10.2Preliminary Analysis of Biological Fluids

location. Another red line appearing at a different location shows that the test has worked correctly. Some components of the test kit are immobilized on a membrane that is fixed in the cassette. The sample specimen is a liquid, and when it is inserted into the cassette, it can migrate along the membrane. As it does so, it comes into contact with the immobilized chemi- cals. These test cassettes provide a quick, reliable, convenient way to conduct this test.

Other Body Fluid Tests Other body fluids most commonly encountered in the forensic lab are semen, vaginal secre- tions, saliva, and occasionally urine or fecal material. There are presumptive tests for each of these fluids, but there are confirmatory tests available only for semen. As a result, the labora- tory must report that tests for saliva, vaginal secretions, urine, or fecal material are indicative of those materials, meaning that their presence cannot be confirmed by the tests in common use. DNA technology can provide confirmatory tests for these other types of body fluids, but for now, these are not in common use in most laboratories. Research is progressing in this area, with the aim of finding sensitive confirmatory tests for other bodily fluids.

DNA in sufficient quantities for profiling can generally be obtained from semen, vaginal secre- tion, and saliva traces and stains. Sometimes it can also be obtained from urine or fecal mate- rial traces. To interpret the lab test results properly in terms of the case, it is necessary to try to identify which body fluids, if any, are present in the evidence. That is, it is not enough to do DNA profiling alone and skip the identification tests.

Semen and Vaginal Secretions In sexual assault cases, the forensic scientist looks for semen and seminal stains. This is done partly by microscopy and partly by testing for substances found in human semen. Semen is the male reproductive fluid. It contains spermatozoa, male reproductive cells, in very large numbers. The spermatozoa are produced in the testes and migrate through a duct called the vas deferens to the seminal vesicles. When a man undergoes a vasectomy to become ster- ile, the vas deferens tubes are cut and/or tied. The liquid portion of semen, called seminal fluid, is produced mainly by the prostate gland. During ejaculation, the spermatozoa and the seminal fluid mix to form semen. One of the specimens the lab examines for semen in a sexual assault case is the vaginal swab. Other specimens include stains on almost any object or sur- face, or swabbings of those stains. Sometimes, semen stains can be seen by the eye in regular light. But they may be difficult to discern on dark textiles or surfaces. Analysts can use fluo- rescent and certain other narrow wavelength lights to help find these stains. These lights can be used in the field if necessary as well.

Identifying semen in the laboratory consists of identifying spermatozoa under the microscope or detecting proteins known to be highly associated with or unique to seminal fluid. These proteins are mainly prostate specific antigen (PSA) (often called p30 by forensic scientists) and seminogelin. Some men do not have sperm in their semen, due to a medical condition or because they have had a vasectomy. Semen from such men must be identified using tests for the proteins. The seminogelin test is confirmatory for semen. Until quite recently, PSA was considered confirmatory as well. It has been found that there is a very small quantity of PSA in certain female internal reproductive tissues and in breast milk. This finding has caused some labs to report a positive PSA test as “presumptive.”

Section 10.2Preliminary Analysis of Biological Fluids

There is an old test called the acid phosphatase test that is used to screen specimens for the presence of semen. Although semen contains a large amount of acid phosphatase, this test is presumptive, because other things besides semen can contain acid phosphatase. If the presumptive test is positive, a confirmatory test is run. If this test finds spermatozoa and/ or identifies the appropriate semen-specific proteins, it proves that semen is present in the specimen.

There are no specific tests for vaginal secretions. These secretions contain large numbers of epithelial cells, and some laboratories have looked for these cells under the microscope as an indicator of vaginal secretions. However, these epithelial cells cannot be distinguished from those originating from other bodily orifices such as the oral cavity, so this is not considered a test.

Saliva Saliva is the fluid produced by the salivary glands lining the mouth. It lubricates the mouth and contains enzymes that aid in digesting food. It contains other proteins and substances that are involved in protecting teeth from decay. Laboratories may look for saliva in cases in which there is reasonable suspicion of its presence. It is expected to be present on cigarette butts and may be present in cases involving oral sexual contact.

The most common presumptive test for saliva relies on the enzyme amylase. Amylase helps digest starch, but it is not unique to saliva. It is also produced in the pancreas and secreted into the large intestine. As a result, it is found in large quantities in fecal material. There is no confirmatory test for saliva. There are different ways of setting up the amylase test, but per- haps the most common involves using starch that has been incorporated with a blue dye. As the amylase digests the starch, the blue dye is liberated into solution.

Urine and Fecal Material There are presumptive tests for both urine and fecal material, but no confirmatory tests. Pre- liminary tests for urine consist of looking for either urea or creatinine. Both of these com- pounds are present in urine and can be detected by chemical tests. Fecal material contains a bile pigment called urobilinogen, and there is a test to detect it. These body fluids are not as common in forensic labs as the others discussed above, but occasionally the lab must test for them if they are suspected of being present in evidence items and are important for the case.

Molecular Methods As mentioned briefly above, there is recent data from forensic science researchers that meth- ods similar to those for profiling DNA may be useful in identifying and differentiating body fluids by tissue of origin. These methods employ another nucleic acid that is similar to DNA called ribonucleic acid, or RNA. You may recall from biology that DNA is the template genetic information molecule. It contains the information that tells a cell which proteins it should make, among other things. The way DNA does this is by transferring its coded information to another molecule, called RNA. RNA then becomes the template for making proteins. DNA is in the cells’ nucleus and is always there. RNA, on the other hand, is made as needed and is

Section 10.2Preliminary Analysis of Biological Fluids

short lived. It moves from the cell’s nucleus out to the cell’s cytoplasm, where proteins are made. Almost as soon as a protein is made, the template RNA for it is gone. However, if we could “capture” some of this RNA using molecular methods, we could tell if it were present or absent. Different tissues and cells have different proteins in them. Thus, different RNAs will be present in each type of tissue. If we could find a protein in a tissue that is unique, then that tissue should have a unique RNA that we could find. That is the basis for these new methods.

The data so far suggest that these methods have great promise, and they may come into wider use as they are validated and incorporated into lab protocols.

Species Determination of Biological Fluids Part of the identification steps involved in the preliminary examination of blood and body fluids is testing to determine if the specimen is human. Labs do not generally test body fluid specimens for species, because it is usually clear from the context. In cases in which it is not clear, labs are capable of running such tests, which are similar to species tests for blood.

Nonhuman blood is sometimes encountered in casework. The most common example is a hit-and-run. A vehicle may become suspect in a hit-and-run case, and blood might be found on its bumper or undercarriage. The owner or driver may think it is from an animal. Since it is possible that the blood belongs to an animal, testing must be done.

The lab can test for many common farm animal and household pet bloods, in addition to human blood. Recall the earlier discussion on antigens and antibodies and the fact that scien- tists can make antibodies to be used for testing purposes. So, for example, “antihuman,” “anti- dog,” and “anticow” antibodies can be made and used to test forensic evidence specimens. There are several different ways of setting up these antigen–antibody tests. In one method, a gel is made and holes punched into it. You could think of a gel as being like Jell-O; molecules can move around in it. Little holes are punched into the gel, and an antibody is put in one hole and the specimen in the other. If the molecules are allowed to diffuse in the gel for a while, they will encounter one another. If the antibody recognizes the specimen (antihuman recognizes human, antidog recognizes dog, etc.), a visible precipitate forms that the analyst can see. This process may not be able to test for more exotic species, but there are specialized labs that can do so if necessary. Some of the traditional immunological species tests cannot distinguish between human and higher primate bloods (such as chimpanzees). Normally, that is not a problem.

Think About It

Do you think that if molecular methods using RNA prove to be useful in identifying and differentiating body fluids, the older testing methods won’t be necessary? How could this change laboratory analysis and cases that involve biological fluids? How would it help in interpreting the meaning of the evidence?

Section 10.3Sexual Assault

We mentioned immunochromatographic tests that test for human hemoglobin. As noted, this test is both a confirmatory test for blood and a human species test. When this test is positive, the specimen is human blood. But if the blood is from some other species, this test will be negative. These commercial immunochromatographic test cassettes are only made to test for some- thing being human. They are not available to test for different animal bloods. So if animal blood is suspected, the lab has to use one of the older methods to conduct the test.

As in the situation described earlier for devising confirmatory tests for particular body tissues or fluids, molecular methods have changed the landscape. If DNA profil- ing is completed on a specimen, part of the preliminary workup consists of establishing how much human DNA is in the specimen. This analysis is an indirect species test that establishes that human DNA is in the specimen. The method used to quantitate DNA in the specimen is human specific. If forensic scientists know the specimen is blood, they can confirm that it is human blood if human DNA is extracted from the blood. If the goal is to show that the specimen is human, this strategy works well. But, for example, if you happened to have a mixture of human and dog blood, you could establish that human blood was indeed present, but you wouldn’t get any information that there was dog blood there. With body fluid stain specimens, the DNA analysis can establish that human DNA is present, but it does not reveal what the specimen is. For example, a vaginal swab from a woman who alleges that someone assaulted her by means of oral sex may test positive for amylase. The results suggest, but do not prove, that saliva is present. Showing that human DNA is present in the specimen is of no help in identifying its source. It could be all vaginal cell DNA or a mixture of vaginal cell and buccal cell DNA. Even if the DNA typing showed that there was indeed a mixture of two people, one of them the woman, we would still not have any information about how the second person’s DNA got into the specimen. This example leads us to our next topic, sexual assault cases.

10.3 Sexual Assault Sexual assault investigation generates a large number of cases in the biology section of the laboratory. In some labs the number of sexual assault cases coming into the lab is greater than the number of blood cases.

Most of the time, a sexual assault case that comes to the laboratory contains a sexual assault evidence collection kit. The case may or may not have a suspect, or person of interest. In cases in which the complainant knows the person, he or she can tell the investigators who it is. In cases of a stranger, the victim will not know the person’s identity and may not have clearly seen the suspect to provide a description of facial features to investigators.

AUBERT/BSIP/SuperStock Biological fluids found at a crime scene cannot be assumed to be human. Luckily, for blood specimens, this can be confirmed using immunochromatographic tests. Do you know of other tests that can be used to show that a dried blood specimen is human?

Section 10.3Sexual Assault

Types of Sexual Assaults There are a few different types of sexual assault cases. One type involves children or underage youths. Children may be subjected to various kinds of sexual abuse, but these cases do not usually reach the forensic laboratory. This is because the abuse may not be rape, and children generally do not report these incidents right away. Instead, these cases tend to be handled by specialized investigators. Sexual assault that involves adults or older underage youths may be perpetrated by either a stranger or someone they know. Every state has a defined age after which a person can give consent for sexual activity. If he or she has not reached this age and is a victim of sexual assault, the law considers it a crime of rape. This is sometimes called statutory rape. In these cases the prosecutor need only prove that sexual activity occurred. There are also cases involving victims with limited mental status. They too are unable to give consent. There are also many cases in which it is questionable whether a complainant could give consent because of impairment due to alcohol or drugs.

With people over the age of consent, the cases differ only as to whether they know the sus- pect. If they do, the suspect often does not deny the sexual activity but states that it was con- sensual. These cases are called consent cases. Here, the fact that sexual penetration occurred and that the suspect’s DNA is found on a swab does not help decide the case. The lab findings are the same whether consent was given or not. In stranger cases the DNA testing is much more important. Its profile may be matched to a suspect if there is one, or it might be found in the Combined DNA Indexing System (CODIS) DNA profile database. In recent years, the number of consent cases has exceeded the number of stranger cases. These may also be called date rape or acquaintance rape.

The majority of sexual assault cases that come to the attention of forensic labs are assaults of women by men. There certainly are cases of men assaulting other men. And there are cases of adults of either gender assaulting underage persons of either gender.

Backlogs There are backlogs of sexual assault evi- dence kits both in police departments and in forensic labs. In recent years the U.S. Department of Justice has been pay- ing attention to this problem and has pro- vided considerable federal grant support to help in reducing the backlog. Kits may not be worked if there is no suspect, since kits from cases with suspects usually take priority. Other times the complain- ant decides not to move forward with the case after the kit has been collected. Some cases may not get worked unless there are ongoing legal proceedings, prompting the lab to prioritize this evidence because the results will be needed soon for a court proceeding.

Associated Press There are many reasons that have led to the extensive number of sexual assault case backlogs. While some work has been done to reduce the backlog, it is still a prevalent issue.

Section 10.3Sexual Assault

Once DNA profiling and the CODIS database were established, many jurisdictions realized that there were older sexual assault evidence collection kits that had never been worked. In order for CODIS to be useful in connecting cases or solving nonsuspect cases, the DNA profiles must be included. Because of this, many jurisdictions hired contract DNA labs to work through their sexual assault kit backlogs and enter any DNA profiles into CODIS. There is still work to be done on this front, but the effort is paying off in establishing connections between old cases and in solving others. In a detailed study of this issue in Los Angeles, Peterson, Johnson, Herz, Graziano, and Oehler (2012) looked at a sample of kits from both the city and county that had never been submitted to the lab but were sent to a contract lab for analysis. This backlog was in the police agencies, not the lab. In this study, entering what DNA profiles could be obtained from the evidence into CODIS resulted in some new information (hits to other cases) but also led to information that already existed. For example, a suspect might have been convicted without kit analysis (and thus entered into CODIS), and when the kit evidence profile was searched, it found the suspect. The results of the study are informative, but more complex than one might think at first glance.

Sexual Assault Nurse Examiners and Sexual Assault Response Teams About 20 to 25 years ago, sexual assault case investigation became better coordinated among police, prosecutors, medical personnel, and laboratories. This was a result of the develop- ment of the SANE concept, created by two nurse professor-practitioners, Dr. Linda Ledray and Virginia Lynch. The nurses leading the SANE effort understood that tending to sexual assault complainants was a low priority in the emergency rooms in which they were seen and that hospital staff were not trained in the examinations of these complainants. Forensic nurses are trained in these examinations, as well as evidence collection, which can help move sexual assault cases through the system more expeditiously and efficiently. There are now SANE clin- ics that treat only sexual assault complainants, a strategy that works well in the complainant’s treatment and in moving legal cases forward.

The same pioneers also actualized the concept of a sexual assault response team (SART), consisting of a forensic nurse, prosecutor, forensic lab person, victim-services representative, and law enforcement. The SART idea goes hand-in-hand with the SANE idea, and they are often referred to collectively as SANE/SART. SART coordinates the activities of the involved parties in a sexual assault investigation to collaborate and formulate a plan in advance for what happens when a complainant comes forward. The plan includes everyone’s respective

Think About It

It was mentioned that until quite recently there were a large number of sexual assault evidence collection kits in police agency property rooms that had never been submitted to the forensic lab. Why do you think this was? What are some reasons why the lab has not worked on the evidence?

Section 10.4Collection and Preservation of Sexual Assault Evidence

roles and duties and also involves devising a sexual assault evidence collection kit that will be standard and used throughout the jurisdiction. In most places, a sexual assault complain- ant may go or be taken to almost any emergency room or clinic, so it is important to have this coordination. In some places, the forensic nurses have separate stand-alone clinical facilities for sexual assault complainants, or they may travel to the complainant. You can read much more about this effort in Ledray (1999).

10.4 Collection and Preservation of Sexual Assault Evidence

It’s important to mention that throughout this discussion, the complainant or victim of a sex- ual assault is often referred to as “she” and the suspect or offender as “he.” This is a typical situation. However, as noted earlier, there are also sexual assaults of men by other men, which are sometimes reported.

In most cases involving adults and sexually mature girls, even if the latter are under the age of consent, the investigation begins with police. If the police think the case needs further investigation, they open a case file. This is called founding the case. If the assault is recent, the complainant will be offered the opportunity to visit a clinic for examination. If she refuses, the case is not likely to move forward. She will also make a statement to the police regarding the events that occurred. At this stage the complainant may simply decide not to go forward with the complaint. Or she may decide not to go forward after the complaint has been taken and the sexual assault kit collected.

At the clinic, the complainant is examined for trauma and injuries and may be treated. She may also be tested for sexually transmitted diseases (STDs) and for pregnancy. In many cases it is too soon after the sexual activity to detect the presence of pregnancy or STDs, so there will be follow-up later on. It is important to document trauma and injuries at this clinic visit, because later on, if the case proceeds, there may be no visual evidence of it. Although clinics that see sexual assault complainants strive for follow-up visits, usually some weeks after the initial visit, to discuss the results of STD and pregnancy tests and to suggest other follow-up care, many complainants are lost to follow-up. They don’t come back or contact the clinic again. For this reason, some clinics believe that the complainant should be treated for pos- sible STDs and for possible pregnancy even without knowing whether either of these condi- tions exists.

With the complainant’s consent, a sexual assault evidence collection kit will be taken as well and submitted to the forensic lab. Her clothing is also generally collected as evidence and new clothing provided to her. The clothing of interest is what she was wearing at the time of the assault.

The forensic science laboratory’s role in this process is examination of the clothing, sexual assault evidence collection kit, and any other evidence that is submitted. The lab’s findings are reported to the submitting police agency and to the prosecutor’s office.

Section 10.4Collection and Preservation of Sexual Assault Evidence

Sexual Assault Evidence Collection Kits Collecting the evidence by means of a sex- ual assault evidence collection kit is another step in the process. As noted ear- lier, these evidence collection kits are usu- ally jurisdiction specific, having been designed by a coordinating committee. They differ in the details, but they also have many things in common.

Most kits contain provisions for collect- ing the following items. Everything has its own non-airtight container with space for labeling to ensure chain of custody.

• consent papers for the complainant

• sketch forms for the clinician to note any injuries, marks, or evidence locations • packages for clothing • packages for miscellaneous evidence, like trace materials, soil, body fluid stains on

the complainant’s body, and so on • vaginal, oral, and anal swabs • vaginal, oral, and anal slides • buccal swab (a swabbing of the inside of the cheek) • complainant’s known head hair • complainant’s pubic hair combings • complainant’s known pubic hair

Remember that the purpose of collecting these items is to (a) help establish that a sexual assault occurred and (b) associate or dissociate the accused with the complainant by confirm- ing that his body fluids and DNA were or were not in the complainant’s body. Finding semen or DNA on a body cavity swab establishes that penetration occurred, which is one element of sexual assault. Remember that these results are the same in cases of consensual sex.

Sometimes head or pubic hair transfers may occur, which is why known and combed hairs should be collected. Details on how to properly collect these samples were discussed in Chap- ter 6.2. It’s also important to remember that hair comparison is not a positive means of iden- tification, but hair can be a source of mitochondrial DNA. Mitochondrial DNA typing is not a positive means of identification, but it may be useful if there is no source of nuclear DNA in the case. Hair can also have exclusionary value, which can make it possible to say that a hair did not come from a suspect or complainant.

In most jurisdictions, there is a time limit for collection of a sexual assault kit, which averages from 72 to 96 hours. If the time limit is exceeded, a kit will not be taken, because the evidence within the complainant’s body is likely to be gone by then. This time limit is not usually an absolute but a guideline to be followed by investigators. Clothing may still be collected if it

Elaine Thompson/Associated Press There is no standard sexual assault evidence collection kit, but most have the same basic components. Why do you think there are variations from jurisdiction to jurisdiction?

Section 10.4Collection and Preservation of Sexual Assault Evidence

is available. Clothing is important, because it may contain stains. Collecting other items, like bed sheets, sofa covers, car seats, and so on, can be important as well, depending on where the incident took place.

Another action that clinicians should take with a complainant is description and documenta- tion (photographs and written descriptions) of injuries. This is important, because the inju- ries will likely be healed by the time the case is prepared for court.

We have up to now described what might be called victim’s sexual assault kits, but there are kits for suspects (usually males) as well. Sometimes they are distinct. Other times, they spec- ify different instructions using the same kit contents. Either way, a known buccal swab (for DNA) must be collected, along with clothing, known head and pubic hair, and a penile swab if the time between the incident and the collection is short.

Alcohol and Drug-Facilitated Sexual Assaults An element of the sexual assault investigation discussion that has surfaced in recent years is drug facilitation. This means that the victim of the assault is impaired by drugs and may be unable to give consent. Many drugs may be implicated in sexual assaults, including drugs that a victim takes by prescription. However, the ones that receive the most attention are flunitraz- epam (Rohypnol), ketamine, and gamma hydroxybutyrate (GHB), which are legitimate drugs for certain specified uses. Rohypnol is banned in the United States because of its involvement in drug-facilitated sexual assault, but it is available in most other countries. These drugs ren- der a person sleepy and unable to think clearly and also tend to affect the memory, making the person unable to remember events that took place.

Laws against giving someone any drugs for the purpose of making them compliant for sexual activity are in place federally and in every state. In cases in which drugging is a possibility, a urine or blood specimen may be taken from the complainant at the time of the medical exami- nation and submitted to a forensic toxicology lab, as described in Chapter 5.5. One problem is that detection of drugs in blood or urine does not tell the analyst how the drug got into the complainant’s body. It is known that people self-abuse these drugs, so a complainant may have chosen to take the drug. That doesn’t change anything in terms of a drug-facilitated sexual assault, but a positive drug test does not establish that someone gave it to her.

Think About It

Because there are backlogs in labs, they sometimes examine only the vaginal swab. They look to see if semen is present, and if it is, they proceed to DNA typing. When contract labs are asked to examine a large number of previously unopened kits, they do the same thing. Do you think that taking this “shortcut” is good practice? Why or why not? What informa- tion might we get from examining all the other evidence in the kit that could be helpful in resolving the case?

Conclusion

Alcohol has also been a factor in many sexual assault cases. Often, both parties have been drinking. The term alcohol-facilitated sexual assault is now used to indicate that a complain- ant is impaired by alcohol to the extent that consent cannot be given.

Conclusion Blood patterns are an important category of pattern evidence, used primarily for reconstruc- tion of events. Blood patterns at scenes can show investigators what types of events caused their formation. In turn, the types of events predicted by the blood patterns can be used in formulating a reconstruction of the violent events.

Before DNA analysis, preliminary testing of blood and body fluid evidence as well as genetic testing was all done together, often by the same person. Now preliminary tests are often done by someone other than a DNA analyst. These tests establish the identity of blood and body flu- ids that are present in the evidence, which occur prior to DNA analysis. This is usually called forensic biology.

The preliminary testing of evidence consists of screening (presumptive) tests and of confir- matory tests. The screening tests are fast and sensitive. Only items that are positive in the screen will be subjected to confirmatory tests for further analysis. Confirmatory tests prove that something is present when they are positive. There are confirmatory tests for blood and semen but not for other body fluids. Developing molecular methods may help solve this prob- lem. Species tests for bloodstain specimens are necessary to show that the blood is human. Sometimes, the lab may be asked to determine what nonhuman species the blood came from. Once in a while, species testing may be required on a body fluid residue other than blood. There are some indirect species testing methods involving DNA.

Investigating sexual assault cases requires special techniques. Special forensic nurses called SANEs and coordination teams called SARTs are especially helpful in implementing thorough- ness and coordination in these investigations. There are quite a few types of sexual assault evidence collection kits in different jurisdictions, but they have many elements in common. The purpose of the kits is to collect evidence so as to protect chain of custody and to help establish the elements of the sexual assault offense. Some sexual assault cases involve alcohol or drugs and may require additional toxicological analysis.

Key Ideas

• Blood leaving the body follows the laws of physics as it moves onto skin surfaces, into the air, or onto other surfaces. That enables forensic scientists to reconstruct the events that led to the blood patterns observed at scenes.

• Bloodstain droplets and patterns can be recognized as low, medium, or high velocity. Their angle of impact can be calculated.

• Many factors, including type of receiving surface, can affect the interpretation of blood patterns.

• The preliminary examination of blood and body fluid stains, which identifies what is present in the stains and the species of origin, is usually called forensic biology. It is distinct from DNA analysis.

Conclusion

• Careful packaging and preservation of dried blood and body fluid stains and collec- tion of appropriate comparison specimens is necessary at a scene.

• Investigators must be aware of potential biological hazards at scenes involving blood or body fluids, as well as strategies for avoiding exposure to them.

• There are preliminary (presumptive) and confirmatory tests for blood and semen. There are only presumptive tests for other body fluids. New molecular methods may help overcome this limitation.

• Bloodstains (and occasionally other body fluid stains) require determination of spe- cies of origin.

• Forensic investigation of sexual assault cases involves coordination of the activities of clinical, lab, police, prosecutor, and victim services personnel.

• In some jurisdictions, there are SANE/SART facilities where sexual assault complain- ants can be seen by forensic nurses.

• Alcohol and certain depressant drugs are sometimes involved in sexual assaults. If these substances render a person unable to give informed consent to sexual activity, then it is called alcohol- or drug-facilitated sexual assault.

Critical-Thinking Questions

1. A serious assault has occurred in a private residence. A man is accused of having beaten another man with a baseball bat about the head and face. This assault hap- pened near a wall, and there is a lot of medium-velocity blood spatter on the wall. The suspect says the victim, who is bigger, was threatening to hurt him and he just defended himself and hit the victim a time or two until he fell down. Other people in the house who are friends of the victim say that the suspect not only hit the victim while he was standing up but continued to beat him after he was down. Explain how the blood patterns would help you as an investigator sort out these two scenarios. Which type of patterns would you expect to see to support these scenarios?

2. In a sexual assault case, the complainant states that the assault occurred in her apartment on a bed that had a mattress on it but no mattress pad nor sheets. The mattress needs to be packaged, collected, and submitted as evidence. How would you go about doing this?

3. You work as a scientist in a forensic lab and are called to testify in court about a case involving blood identification. How would you explain the preliminary and confirma- tory tests for blood to the courtroom?

4. A sexual assault case is being prepared for trial. The alleged assault happened in the suspect’s apartment on a bed. The complainant says she was forced to have sexual intercourse against her will. The suspect says there was sex but that it was consen- sual. The lab findings from all the physical evidence from the scene and the sexual assault evidence collection kit are equally consistent with either version of events. Is there anything else investigators could have or should have done with regard to physical evidence in this case that would help distinguish between the versions?

5. A woman reports to police that she believes she was sexually assaulted. She says she is pretty sure she was drugged because she doesn’t remember anything after being with the suspect early in the evening. Much later, she woke up back at home and realized that an assault may have occurred. She is taken to a clinic for examination and a sexual assault evidence collection kit. The forensic nurses also collect a urine

Conclusion

specimen. The lab reports that there was no semen on the vaginal swab and that it could find no drugs in her urine. The suspect simply says she and the suspect were out but that she wasn’t feeling well and asked to be taken home. Is there anything further, in terms of investigation from a physical evidence point of view, that the police can do to help determine whether there really was a drugging or an assault?

Key Terms amylase An enzyme involved in starch digestion, produced by the salivary glands around the mouth and usually present in high concentrations in saliva.

angle of impact (incidence) The angle at which a blood droplet impacts a target surface.

antibodies Proteins made by animals’ immune systems in direct response to an invading antigen or disease-causing entity.

antigens Substances, often proteins, that can evoke an immune response in an animal.

arterial spurt A blood pattern resulting from blood being pumped out of the body through a severed artery.

biological hazards (biohazards) Infectious agents that can be present in blood or body fluids and can thus pose hazards for people who must handle or come into contact with blood or body fluids.

bloody impressions Any impression in blood; most often refers to bloody finger- prints or palm prints or foot or footwear impressions.

cast-off A type of blood pattern caused by blood droplets being thrown off from a bloody object as it is swung through the air.

catalyst A chemical or substance that speeds up a chemical reaction but is not itself changed in the process of doing so.

chemiluminescence Light resulting from a chemical reaction. An example of a chemilu- minescent substance is luminol, used to test for the presence of blood.

comparison specimen A sample of the unstained surface on which a bloodstain is deposited.

contact transfer A blood pattern on a receiving surface resulting from a bloody object contacting that receiving surface.

enzyme A protein in the body (or in any living cell) that acts as a catalyst.

hemoglobin The molecule in red blood cells that transports oxygen to body tissues from the lungs.

high-velocity A blood pattern resulting from high-intensity force acting on the blood and blood droplets, typically from gunshots or explosions.

low-velocity A blood pattern resulting only from the force of gravity on the droplets.

medium-velocity A blood pattern result- ing from intermediate-intensity force acting on the blood and blood droplets. A good example is the blood pattern from multiple blunt-force strikes to the head.

movements (trails) The blood patterns from which the movement of the source can be discerned.

plasma The liquid part of blood.

Conclusion

platelets Cell-like structures in the blood that are involved in clotting.

running A blood pattern in which blood hits a vertical surface, then runs downward.

satellites Small, peripheral droplets sur- rounding a central bloodstain droplet, the result of the main droplet striking a nonab- sorbent surface with sufficient force.

secondary spatter A medium-velocity blood pattern caused by blood droplets fall- ing into a preexisting pool of liquid blood, causing it to spatter.

semen A mixture of spermatozoa and semi- nal fluid, ejaculated by a male at his sexual climax.

seminal fluid The fluid with which the spermatozoa is mixed in the male reproduc- tive system prior to ejaculation. Most of the seminal fluid volume is produced by the prostate gland.

sexual assault response team (SART) Usually, this program goes hand in hand with forensic nurses.

spermatozoa Male reproductive cells.

subspecimens Specimens cut or otherwise derived from a larger, intact specimen, such as cuttings of bloodstains from clothing or a carpet.

swipe A bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with char- acteristics that indicate relative motion between the two surfaces.

wipe An altered bloodstain pattern result- ing from an object moving through a preex- isting wet bloodstain.

Web Resources Website for the International Association of Bloodstain Pattern Analysts: http://www.iabpa.org

A proposed standard for blood pattern terminology may be found at: https://www.nist.gov/sites/default/files/documents/2017/11/15/bpa_terms_and _definitions_in_bloodstain_pattern_analysis.pdf

A guide to the setup and operation of a SANE program by Linda Ledray: http://www.niccsa.org/uploads/file/0612da19f5484fa28deb8fd97c2cc457/SANE DEVELOPMENTANDOPERATIONGUIDE.pdf

National Institute of Justice resource on untested sexual assault evidence kits: http://www.nij.gov/nij/topics/law-enforcement/investigations/handling-evidence/ untested-sexual-assault.htm