CRJS406 IP week three

Collecting Evidence

CRJS406-IP3

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Collecting Evidence at Crime Scene

Once a crime scene is properly secured and the initial walk through has been conducted the collection of the evidence located during the walk through will be commence. Evidence is essential to providing the police with the clues they need to determine who committed the crime and to prove in a court of law a criminal defendant is guilty of the crime they are accused. While evidence can be collected at the crime scene if it is not properly collected and documented it will not be eligible for a court of law. Each type of evidence located at the crime scene can provide valuable information about the crime.

Once physical evidence is located at a crime scene it must be documented were it sits. How evidence is documented is through sketches and photographs. The crime scene collector will place an evidence marker by the evidence and take photographs from every angle to show the court where the evidence was located at the scene. The evidence is then collected using the established uniform standards and properly packaging the evidence for transportation to the lab. This includes properly labeling the container the evidence is packaged in.

Explosives

When collecting evidence at a crime scene some evidence is extremely volatile and dangerous and must be handled carefully. If the scene contains actual explosive the scene will be evacuated and a bomb squad will be called to remove the dangerous evidence. Once the explosives are removed or if the forensic team is looking for proof an explosive was used at a crime scene they will begin the search for explosive residue. The research for residue involves the use of an alternative light source and knowledge of the different accelerants used at the scene.

Just like in the collection of all evidence once the residue is located through swabbing techniques it will be tested before being transported to the lab. Once the evidence is swabbed it will be placed in a dry, clean envelope. Each swab will be packaged and labeled separately to avoid cross contamination. Potential bomb or explosive fragments are collected using tweezers or gloved hands and placed separately in a dry clean container and properly labeled. When an explosion occurs the evidence comes in the form of tiny fragments. This includes collecting bomb fragments and bomb components.

Computers

Computers have become an important part of everyday life for just about every citizen in the nation. When crimes are committed in the 21st Century the computer can provide an important source of evidence of the criminal investigation. Collecting computers is a delicate process requiring skill and knowledge from the forensic investigator. A long with every piece of evidence collected at the scene the computer needs to be photographed from every possible angle before being collected. Once the evidence has been photographed including the screen of the computer the collection process can begin.

If the computer is one the forensic investigator must collect live data. The investigator will start with RAM image (Live Response locally or remotely via F-Response) and then collect other live data "as required" such as network connection state, logged on users, currently executing processes etc (Henry, 2009). The first thing the forensic investigator must do is turn of the computer once the live data is collected and then disconnect external devices connected to the computer. The computer stack or modem is then removed and each drive is taped shut. The computer evidence is then packaged with evidence tape.

The computer will be totally wrapped in evidence tape before being labeled. The label will contain information including where the computer was located at the scene and who collected the evidence, when the evidence was collected, at what time, etc. Once the computer modem is collected any external devices connected to the computer will be collected and packaged totally separately. Each external device could contain important information pertaining to the crime or the behavior of the criminal defendant.

Fingerprints

Fingerprints are still one of the most valuable pieces of forensic evidence available for law enforcement to identify the criminal offender responsible for committing a crime. Fingerprints are extremely difficult to see and extremely delicate. In order to detect fingerprints on all types of different surfaces different techniques will be used. In order to detect fingerprints on removable objects that is not easily discernible to the eye the forensic investigator will package the object in a clean dry envelope in order to transport it too the lab. If an object can be tested at the lab instead of the scene it will be properly packaged, labeled, and then transported to the forensic lab. These objects must be handled as little as possible but always with gloves.

When fingerprints are located on objects that cannot be removed from the scene the collection of the fingerprints will be lifted from the object and then transported to the lab. How the fingerprint is lifted is dependent on the type of surface the fingerprints needs to be lifted from the scene. Before a print is lifted it must be photographed. In order to develop the fingerprint to make it visible in a photograph it must be developed with dusting powder. The fingerprint is photographed to scale with an evidence marker.

A fingerprint on a dark surface will be dusted with white powder until the entire fingerprint appears. The print is then lifted using tape before being sealed in a clean, dry envelope. Each fingerprint is packaged separately and labeled. The package will identify who lifted the print and where the print was located at the scene as well as date, time, etc. When the fingerprint is located on a white surface black powder is used to highlight the print before it is lifted and placed in a clean evidence envelope.

Most fingerprints submitted will be located on paper, glass, metal, or other smooth surfaced objects. It is harder to collect fingerprints from some surfaces over others. Smooth surfaces yield good fingerprints that are easy to lift but rough surfaces are fair more difficult to yield fingerprints. If the rough surfaced items can be removed it will be collected, packaged, labeled, documented, and then shipped to the lab.

Firearms

When firearms are located at the crime scene it will be collected through the trigger ring using a pencil or other object but only after the gun has been put on safety. The fire arm must be handled with gloves and any bullets must be removed. Bullets can remain in the magazine but the magazine must be removed from the gun as well as any bullets in the chamber. Before the gun can be packaged important information on the gun must first be noted. The forensic investigator will record the serial number, make, model, and caliber of the weapon, and mark it in some inconspicuous manner that does not detract from its value before sending it to the Laboratory (Shapiro, 2009).

Once of all of the important information is recorded and the gun marked t will be packaged in a cardboard evidence box. Guns can be heavy requiring a strong evidence collection box and to prevent it from falling out or moving around. If the weapon is a rifle or a shotgun it will not be broken down but will be transported in a cardboard box. If there is blood, trace, or fingerprints on the weapon paper must be line the box first to preserve this evidence. Fingerprints can be collected at the scene following the provided collection standards.

Bullets are collected and placed in an envelope separate from the gun. All recovered bullets are first wrapped in paper and sealed in a separate labeled pill box or envelope (). The bullets are wrapped in paper in case they contain evidence. Bullets can provide forensic investigators with valuable information about the gun and any bullets used at the scene. Once the bullets are placed in the evidence envelope they are labeled with the necessary information to protect the chain of evidence.

Fibers

Fibers and threads are on clothing, carpet, furniture, and bedding. These fibers can connect a criminal suspect to a crime scene or a victim to a criminals suspect. When fibers are located they can be picked up with fingers or tweezers. Once the fiber is collected it is placed in a small coin envelope. Never place loose fibers directly into a mailing envelope since they can be lost from this type of envelope (Shapiro, 2006). Since fibers are not always visible to the eye they are also collected by taking tape and lifting any fibers on items associated to the crime.

For example tape would be used to lift fibers and hair from the clothes of a murder victim or the chairs in a criminal suspect’s car. Fibers are valuable pieces of evidence tying a suspect to a victim. If a fiber from the suspect’s shirt is matched to a fiber found in the hair of the victim this shows the suspect has had close contact with the victim. Fibers tie two scene together by showing a suspect was in the victim’s home because unique fibers from a blanket in the home were found on the clothes of the suspect.

Impressions

Fingerprints are only one form of impression that is collected at a crime scene. When criminal suspects are at a crime scene they leave behind evidence they were present at the scene. The two most common impressions beside fingerprints at the crime scene are tire impressions and footwear impressions. The tire impression is collected different if it is located on a hard surface over the soft surface. Before the tire or footwear impression can be collected it must be photographed. In some case the photographic can be used to match the impression evidence to the tire or footwear.

If a tire or footwear impression is left on a soft surface it will be filled with dental stone and left to dry. Once the dental stone dries the impression left behind on the dental stone is collected. If the soil is soft or sandy, first use hairspray to firm it up so that you’ll be able to lift the cast (Fuller, 2010). If the impression is being lifted from snow the forensic investigator will first place snow print wax into the impression. The collected dental stone will be placed in a large, cardboard evidence box if the impression is from a tire impression and a smaller cardboard box if the impression lifted was from footwear.

When collecting the tire or footwear impression evidence from a hard surface a completely different procedure will be followed. Photographs to scale are very important in the collection of impressions from hard surfaces. Tire and footwear impressions on hard surfaces are collecting using fingerprint electrostatic powder and lifting the impression with tape. This is far more difficult than with a fingerprint due to the size of the objects. The evidence once collected is placed in evidence enveloped and labeled.

Tool Marks

Tool marks are a form of impression evidence. When a criminal uses a tool to alter evidence or to cause damage to a victim or property the marks left by the tool used provides evidence to the criminal investigator. For example if a criminal uses a screwdriver to pry open a window the evidence left behind can then be used to math to the tool. The tool leaves a fingerprint behind allowing the criminal investigator to match them to a specific weapon used in a crime. In many cases, it is possible to identify the specific tool which made the questioned marks by means of a Laboratory comparison of tools and marked objects (Shapiro, 2006).

Tool marks are left behind on objects at the crime scene making the evidence harder to collect. The marking left on the window sill or door jamb must be photographed carefully to ensure there is sufficient evidence to match a tool. Any evidence continued around the tool marking, such as paint chips should be collected. Any tools at the scene should also be collected and packaged separately and later matched to the marking at the scene.

Each piece of evidence collected at the scene must be collected following uniform guidelines. These guidelines will protect the chain of evidence and ensure it is eligible or authenticated in a court of law. If the evidence is not properly documented or collected using uniform standards it may be excluded from the court process. Without physical evidence pointing to the criminal’s guilt it is far more difficult to prove they committed the crime. Juries expect forensic evidence pointing to the suspect’s guilt.

References

Fuller, J. (2010). Impression Evidence -- Footprints, Tire Tread and Tool Marks. Retrieved

October 27, 2013 from http://science.howstuffworks.com/impression-evidence1.htm

Henry, P. (2009). Best Practices in Digital Evidence Collection. Retrieved October 27, 2013

from http://computer-forensics.sans.org/blog/2009/09/12/best-practices-in-digital-evidence

Shapiro, G. (2006). Evidence Collection Guidelines. Retrieved October 27, 2013 from

http://www.crime-scene-investigator.net/collect.html#4