Physical Matching
If we think back to the example in Chapter 1 where the Bow Street Runners (McCrery, 2013)
made a physical match from the torn edges of one piece of wadding paper to the original sheet
from which it was torn, we can appreciate that physical matching is a forensic technique that can
be applied, to some extent, by the investigator personally viewing and studying details of the
evidence. At this level, physical matching can be used by investigators to do on site analysis of
evidence. That said, the more sophisticated aspects of physical matching do require the expertise
of a person trained in the techniques to form and articulate an opinion that the court will accept
as expert evidence.
During a crime investigation, physical matching is typically conducted on items, such as
fingerprints, shoe prints, tire prints, glove prints, tool impressions, broken glass, plastic
fragments, and torn edges of items, such as paper, tape, or cloth. In these physical matchings,
there are two levels of examination that are typically considered; an examination for class
characteristics and an examination for accidental characteristics.
Level One – The Examination of the Item for Class Characteristics
Determining class characteristics takes place in relation to items, such as shoe prints, tire prints,
glove prints, and tool impressions. At the first level of examination, these items can be classified
and sorted based on type, make, model, size, and pattern. For example, if a shoe print is found at
the scene of a crime and is determined to be a left shoe of a size 9, Nike brand, Air Jordan model,
running type shoe with a wavy horizontal sole pattern, these class characteristics collectively
provide a description of the suspect’s shoe based on five defined descriptors.
In turn, these class characteristics may allow the investigators to narrow their focus to suspects
having that class description of shoe. It is not a positive identification of the shoe to any
particular suspect, but it does allow the potential elimination of suspects who wear different
sizes, brands, and sole patterns of running shoe. Using this Level One examination, an
investigator at the crime scene may find a suspect shoe print showing a distinct size and sole
pattern. If a suspect with a matching size and sole pattern is found near the crime scene, this
Level One observation would provide strong circumstantial evidence to assist in forming
reasonable grounds to suspect that this person was involved in this crime.
A Level Two examination may be able to produce a conclusive match. Positive identification
requires this next level of examination, namely the examination for accidental characteristics.
Level Two – Accidental Characteristics
Accidental characteristics are the unique marks and features that develop on any item resulting
from wear and tear. Looking back at the Nike Air Jordan Running Shoe, to make a positive
match of a suspect’s shoe to the impression found at the crime scene, the crime scene impression
would be examined for nicks, gouges, and wear patterns typically present on a worn shoe. These
features would then be compared to a rolled impression of a suspect’s shoe, and if the same
nicks, gouges, and wear patterns could be shown in all the same locations on the suspect’s shoe,
a positive match could be made.
This Level Two method of comparison for things, such as shoes prints, tire prints, glove prints,
and tool impressions, is the practice for physical matching. Investigators can often use these
physical matchings to link the suspect back to the crime scene or the victim. Finding a suspect in
possession of a shoe, a tire, or a tool that is a positive match to an impression at the criminal
event is a powerful piece of circumstantial evidence.
With items, such as broken glass and plastic fragments, the process of physical matching requires
significantly greater levels of expertise. At Level One, these items are first matched for general
characteristics, such as material colour and thickness; however, the process for making the
comparison of broken edges requires microscopic examination and photographic overlay
comparison of broken edge features to demonstrate a positive match. For investigators, these
kind of comparisons can be called upon where there is broken glass at a crime scene and
fragments of glass have been found on a suspect’s clothing, or in cases where glass or plastic
fragments are left at the scene of a hit-and-run car crash and a suspect vehicle is found with
damage that includes similarly broken items. Glass fracture analysis can also be used to
demonstrate which side of a piece of glass received the impact that caused the fracture. This can
be a helpful tool in confirming or challenging a version of events, such as insurance fraud, break-
in reports, and motor vehicle crashes where the damage has been exaggerated or staged. Glass
fracture analysis can also be used to demonstrate the sequence and order in which a series of
bullets have passed through the glass of a window. This can be helpful for an investigator to
establish the origin location of the shooter, and, in cases of a drive-by shooting, the direction of
travel.
Topic 2: Fingerprint Matching
The forensic science of fingerprints has a longstanding history in policing. Fingerprints have
been accepted as being individually unique to each person. The courts frequently accept positive
fingerprint matches conducted by an expert witness, as proof of identity beyond a reasonable
doubt (Jain, 2010).
Prior to the modern advent of DNA analysis and biometric scanning technologies for positive
identification, fingerprints and dental record x-rays were the only truly positive means of making
a conclusive identification.
Fingerprints are unique patterns of lines and ridges that exist on the areas of our hands and
fingertips, known as the plantar surfaces. These unique patterns have been classified in
categories and features since the late 1800’s (Dass, 2016). The various categories and features
allow each digit of a person’s fingers to be catalogued in a searchable system or database. These
unique categories and features do not change throughout a person’s life, unless they are
subjected to damage through physical injury or intentional abrasion. The impressions of our
fingerprints are often left on items we touch because the oils our bodies produce act like an
invisible ink adhering to smooth surfaces we touch, thus transferring these fingerprint
impressions to those surfaces. These virtually invisible image transfers are commonly called
latent fingerprints, and they are easily made visible on most surfaces through the application of
colored fingerprinting powder that adheres to the oils left by our fingers. The powder sticking to
the oil reveals the image of lines and ridges that make up the fingerprint. It is also possible for a
fingerprint impression to be exposed on surfaces, such as plastic, dry paper, or paint though a
process of chemical fuming that reacts with the oils of the fingerprint changing their color,
thereby exposing the image. Fingerprints are sometimes also visible when they are transferred to
an object because the finger has some foreign material on it, such as ink or blood. Other forms of
visible fingerprints can be found as an actual moulded impression of the fingerprint when a
person touches a malleable surface, such as clay or cheese.
The unique lines and ridges of an unknown fingerprint can be searched in a database of known
criminal fingerprints for identification. Today, this type of search is done electronically using a
biometric scanning process known as Automated Fingerprint Identification System (AFIS). For
smaller partial prints, identification of a suspect requires sorting through possible suspects and
conducting specific searches of print characteristics to make a match. If the person who left the
print does not have a criminal record or their fingerprints are not on file, the only way a
comparison can be made is to obtain a set of fingerprint impressions from that person. When this
is done, the print examination will be conducted by a trained fingerprint expert who will search
the print to establish as many points of comparison between the suspect print and the known-
print as possible. The general accepted standard for accepting a match is to find ten points of
comparison.
The location and identification of a suspect’s fingerprint at the scene of a crime, or on some
crime-related object, is strong circumstantial evidence from which the court can draw the
inference that the suspect is, in some way, connected to the crime. The investigative challenge of
finding a suspect’s print is to eliminate other possible ways that the print may have been left at
the scene, other than through involvement in the crime.
Hair and Fibre analysis
In considering once again “Locard’s Theory of Evidence Transfer”, (Petherick, 2010) it was
suggested that a person cannot be at the scene of a crime without leaving something behind, and
cannot leave the scene of a crime without taking something with them. Exhibits of hair and fibre
fit support this theory well. As humans, we are constantly shedding materials from our bodies
and our clothing. We enter a room and we leave behind strands of hair that fall from our heads,
oily impressing of our fingerprints as we touch objects, and fibres of our clothing materials. As
we leave a room, we take away hairs from other occupants of the room or fibres from the carpet
and furniture adhering to our clothing. The analysis of hair and fibre, although not an exact
science, can provide corroborative evidence. Hair samples can be compared taking a shed sample
at the crime scene to the hair from a suspect to establish a similarity within a limited degree of
certainty. If the hair happens to have been pulled out and still has root tissue, there is a possibility
for more positive identification using DNA analysis. Somewhat more identifiable than hair
samples, fibre samples can often be narrowed down to make a higher probability comparison
using microscopic examination for size, color, and type between an unknown sample and control
sample.
Ballistic Analysis
Given the number of gun-related crimes, the understanding of ballistic analysis is important for
investigators. Ballistics is the study of all things that are launched into flight, how they are
launched, and how they fly. In most cases, investigators find themselves dealing with several
common types of firearms.
1. Handguns as either semi-automatic pistols or revolvers
2. Long rifles that are single shot bolt action, automatic, or semi-automatic
3. Shotguns that are breach loading or chambered pump action
There are techniques in ballistic science that address the unique aspects of firearms and bullets.
Because ballistic comparisons seek to determine if a particular gun was the originating source of
an unknown bullet or cartridge casing, this examination process is sometimes referred to as
ballistic fingerprinting. The analogy being that if a particular gun touched a particular bullet or
cartridge-casing, it will leave behind some unique identifiable marks or a ballistic fingerprint.
Ballistic Fingerprints
When a modern day firearm is being loaded to fire, the cartridge loaded into the gun is composed
of several components. The bullet portion of the cartridge is tightly pressed into a brass tube,
called the casing. At the bottom of this brass casing is a round, flat base slightly larger than the
casing, and this base prevents the casing from sliding completely into the cartridge chamber of
the gun when being loaded. On the bottom of this flat base of the cartridge is the primer. When
the trigger is pulled, the primer is the portion of the cartridge that will be struck by the firing pin
of the gun. When struck, the primer ignites the gun powder contained inside the brass casing
with an explosion that causes the bullet to leave the casing, travel down the gun barrel, and exit
the gun.
Each of the components of the cartridge casing can be examined forensically and comparisons
can be made to suspect guns. In some instances, it is possible to determine if a cartridge has been
fired from the chamber of a specific gun. This can be done by examining the unique and
identifiable marks left by four aforementioned components of the gun. Like the process of
physical matching, this is also a two-level process.
At Level One, cartridges are classified by the calibre, which is the size of the bullet, the maker
of the cartridge, and the primer location; either a centre-fire or a rim-fire cartridge on the
cartridge base.
For ballistic purposes, guns are classified by their calibre, chambering and ejector mechanisms,
and firing pin, namely either centre-fire or rim-fire. Eliminations of suspect weapons can often
be made at Level One. For instance, a .38 calibre bullet removed from a crime scene cannot have
been fired from a .22 calibre weapon. Or, that same .38 calibre bullet showing marks from an
ejector mechanism could not have been fired from a .38 calibre revolver that does not have an
ejector mechanism.
At Level Two, the more decisive ballistic fingerprint comparisons are often made using the
following methods:
1. Striations Matching;
2. Chamber Markings;
3. Firing-Pin Comparison; and
4. Ejector markings.
1. Striations Matching. Bullets fired from either a handgun or long rifle, other than a
shotgun, fire a single
projectile each time. This fired projectile is a lead or lead-composite bullet. When fired, this
bullet travels down the barrel of the gun and begins to spin because the inside of the gun
barrel has been intentionally machined with long gently turning grooves, called rifling.
These grooves catch the soft-lead sides of the bullet spinning it like a football, and this
spinning makes the bullet travel more straight and true to the target. As a result of these
grooves designed into gun barrels, every bullet fired will arrive at its target with markings
etched into the bullet material from contact with the grooves in the barrel. These etched
markings are call striations, and they are uniquely identifiable back to the gun they were
fired from. For an investigator, these striations create an opportunity to match the bullet to
the gun that fired it. Recovered bullets can be recovered and compared to test bullets fired
from a suspected gun. When striations of a recovered bullet are compared to known
samples fired from a suspected gun, a side-by-side microscopic technique is used to match
striation markings. An expert ballistic examiner can sometimes identify and illustrate
matches in the striations to make a positive match.
2. Cartridge Chamber Markings. When a cartridge is loaded into the chamber of a gun,
the shiny brass casing comes into contact with the hard steel sides of the chamber. This
chambering of the cartridge can leave unique and identifiable scratch marks on the side of
the casing. A cartridge casing ejected or unloaded from a weapon and left at the crime scene
can sometimes be matched to the suspect gun by comparing these markings.
3. Firing Pin Comparison. When the firing pin of any gun strikes the primer on the
bottom of a cartridge, it leaves an indentation mark. This firing pin indentation can
sometimes be matched to the firing pin of a suspect weapon. This requires microscopic
examination that looks for the unique characteristics of the firing pin that become
impressed into the soft metal of the primer when the firing contact happens.
4. Ejector Mechanism Markings. Methods for loading and unloading weapons have
evolved considerably due to different gun designs. The simplest guns allow the user to open
the breach of the gun exposing the cartridge chamber to manually insert the cartridge and
close the breach to make ready for firing. There is no ejector mechanism for these guns, so
there will be no ejector marks left on the base of a cartridge when it is unloaded from the
weapon. Other guns have a variety of different ejector methods, including ejectors that catch
the base of the cartridge casing to physically pull it from the breach and eject them away
from the gun. In cases where a gun does have an ejector mechanism, these mechanisms
leave very distinct and unique marks on the soft brass cartridge base. These markings can
sometimes be compared and matched back to the ejector of a suspect weapon. With this
broad variety of ballistic comparison techniques, an investigator has a significant number of
tools that can be deployed and strategies that can be engaged to assist in matching a bullet to
the gun that fired it. Considering these tools, the cartridge casing left at the scene of a
shooting can be as important as a bullet removed from the body of a shooting victim. An
investigator needs to keep this in mind when seizing cartridge casings as evidence. Great
care needs to be exercised to document the location where each individual casing was
found, and to preserve each casing in a manner that does not degrade the possible markings
that could enable a match to be made. Damage can be done by placing casings into a
common bag where they can rub against each other causing more characteristics and
obliterating existing marks.
Trajectory Analysis
In addition to the ballistic fingerprinting examinations, another area of ballistic science is known
as trajectory analysis. The trajectory of a bullet is the path it travels from the time it leaves the
barrel of the gun to the point where it finally loses the propulsion energy of the gunpowder and
comes to rest. The flight of a bullet can be very short, as in the case of a point blank shooting,
where a victim is shot at very close range, or it can be very distant where the target is one mile
away or more, as in the case in some sniper shootings.
When the bullet is traveling a longer distance, it travels that distance in an arched path or
trajectory of travel as it is pulled towards the ground by gravity. When the bullet arrives at its
destination, it will have a distinct angle of entry into the target. This angle of entry can
sometimes be calculated as trajectory to estimate the geographic location of the originating shot.
In cases where a bullet passes through several objects, such as two walls of a house, the
trajectory of the bullet can be used to determine where the shooter was located. In cases of drive-
by shootings, for example, where several shots are fired, the pattern of trajectories can show if
the shooter was moving and, if so, demonstrate the direction of travel.
Blood Spatter Analysis
Blood spatter analysis, also known as blood stain pattern analysis, is a relatively new forensic
specialty. The purpose of this analysis is to determine the events of a crime where blood has been
shed. This is accomplished through the careful examination of how blood is distributed inside the
crime scene. Studies have shown that when blood is released during an attack, certain patterns of
distribution can be expected (National Science Forensic Technology Center, 2012). For instance,
a person being struck with a baseball bat will begin to bleed, and blood will be distributed in a
droplet spatter pattern in the direction of the strike behind the victim. These droplets of blood
will have a direction of travel that will be indicated by the directional slide of each droplet as the
bat hits objects in its path. Blood from the victim adhering to the bat can also be distributed when
the bat is on the upstroke for the next strike. This blood will be distributed in an upward
directional slide pattern, for example, up a wall, onto a ceiling, or behind the attacker.
Calculations of how many strikes were made may become evident from the tracking of multiple
streams of droplets behind the victim and behind the attacker. Given this developing science,
blood spatter analysis can be useful in criminal event reconstruction.
DNA Analysis
DNA, or deoxyribonucleic acid, is a molecule that holds the genetic blueprint used in the
development, functioning, and reproduction of all living organisms. As such, it carries the unique
genetic information and hereditary characteristics of the cells from which living organism are
formed. Except for identical twins, the DNA profile of each living organism is unique and
distinct from other organisms of the same species. There are some rare cases where one person
may carry two distinct types of DNA, known as Chimera (Rogers, 2016) where paternal twin
embryo merge during gestation, or in cases where a bone marrow transplant enables the
production of the marrow donor DNA in the recipient’s blood. In these rare cases, a person may
test for two distinct DNA profiles for different parts of their body.
In human beings, DNA comparison can enable high probability matches to be made between
discarded bodily substances and the person from whom those substances originated. Bodily
substances containing cellular material, such as blood, semen, seminal fluid, saliva, skin, and
even hair root tissue can often be compared and matched back to its original owner with high
statistical probabilities of comparison (Lindsey, 2003). Sometimes, even very old bodily
substances, such as dried blood, dried saliva, or seminal stains, can be analyzed for a DNA
profile.
The introduction of DNA analysis has allowed investigators for advocates to re-examine
historical evidence and exonerate persons wrongfully convicted and imprisoned for criminal
offences (Macrae, 2015).
DNA is a very powerful tool for investigators and can be considered anytime discarded bodily
material is found at a crime scene. Even very small amounts of material can yield enough
material for DNA comparison. Importantly, DNA data-banks of known criminals and unsolved
crimes are now becoming well established in North America (Royal Canadian Mounted Police,
2006). When a person is convicted of certain criminal offences, DNA is collected and submitted
to these databases.
Forensic Pathology
Forensic Pathology is the process of determining the cause of death by examining the dead body
during an autopsy. An autopsy generally takes place in the pathology department of a hospital. In
the case of a suspicious death or a confirmed homicide, police investigators will be present at an
autopsy to gather information, take photographs, and seize exhibits of a non-medical nature, such
as clothing, bullet fragments, and items that might identify the body. These items would include
personal documents, fingerprints, and DNA samples.
During an autopsy, a forensic pathologist dissects the body carefully examining, documenting,
and analyzing the body parts to determine the cause of death. In the first stage of an autopsy, the
pathologist examines the body for external injuries and indicators of trauma that may provide a
cause of death. In this first stage of examination, the pathologist will make an estimate of the
time-of-death by observing evidence of four common post-mortem (after-death) indicators.
These are body temperature, the degree of rigor mortis, post-mortem lividity, and progress of
decomposition.
Body Temperature
Algor Mortis is the scientific name given to the loss of body temperature after death which can
sometimes be used to estimate the time of death (Guharaj, 2003). This is a viable technique in
cases where the body is being examined within 24 hours following death. This method of
estimating time of death can vary significantly dependent upon many possible variables, such as:
• Ambient room temperature being within a normal range of approximately 22° Celsius
• Pre-death body temperature of the victim not being elevated by illness or exertion
• Thickness of clothing that might insulate the body temperature escape
• The temperature and conductivity of the surface the body was located on that could
artificially increase or decrease temperature loss
Considering a normal body temperature of 37° Celsius at the time of death, it can be estimated
that the body will cool at a rate of 1° – 1.5° Celsius per hour. This calculation is known as the
Glaister Equation (De Saram, Webster,
& Kathirgamatamby, 1956). So, taking an internal rectal temperature and subtracting that from
37° Celsius will provide an estimate of the number of hours that have passed since the time of
death. For example, a dead body with a measured temperature of 34° Celsius would provide a
time range of 3 to 4.5 hours since the time of death.
Rigor Mortis
Rigor mortis is a term used to describe the stiffening of the body muscles after death. A dead
body will go from a flaccid or limp muscle condition to one where all the muscles become
contracted and stiff causing the entire body to become constricted into a fixed position. After
being in a constricted and fixed position, the muscles eventually become flaccid again
(Advameg, Inc., 2017). In normal room temperatures, this stiffening of muscles and the relaxing
again has a predictable time progression of approximately 36 hours. In this progression, the
stiffening of muscles will take approximately 12 hours, the body will remain stiff for 12 hours
and will progressively become flaccid again over the next 12 hours.
Stiffening of muscles begins with the small muscles of the hands and face during the first 2 to 6
hours, and then progresses into the larger muscle groups of the torso, arms, and legs over the
next 6 to 12 hours. These are general rules; however, the rate of rigor mortis can be different for
infants, persons with extreme muscle development, or where extensive muscle activity precedes
death, such as a violent struggle (Cox, 2015).
In determining the time of death in average environmental temperatures, Cox (2015)
recommended that:
1. If the body feels warm and is flaccid, it has been dead for less than 3 hours
2. If the body feels warm and is stiff, it has been dead for 3 to 8 hours
3. If the body feels cold and stiff, it has been dead for 8 to 36 hours
4. If the body feels cold and is flaccid, it has been dead more than 36 hours
Post-Mortem Lividity
Post-mortem lividity refers to a discoloration or staining of the skin of a dead body as the blood
cells settle to the lowest part of the body due to gravity. This discoloration will occur across the
entire lower side of a body; however, in places where parts of the body are in contact with the
floor or another solid object, the flesh compresses and staining will not occur in that area. The
staining is a reddish-purple coloring, and it starts to become visible within 1 hour of death, and
become more pronounced within 4 hours. Within the first 4 hours, lividity stains are not fixed
and, if the body is moved, the blood products will shift and stain the part of the body that has
become lower. In most cases, these stains become fixed between 12 and 24 hours. As such, they
can be viewed as an indicator of how the body was left at the time of death. Importantly, if a
body is found with post-mortem lividity stains not at the lowest point in the body, it can be
concluded that the body has been moved or repositioned after the 12 to 24 hour stain setting
period (Cox, 2015).
Decomposition
This is the final indicator a pathologist can look at to estimate the time of death. Sometimes,
dead bodies are not discovered in time to use body temperature, rigor mortis, or early lividity
indicators to estimate a more exact time of death. In these cases, assessing the progress of
decomposition becomes important. Decomposition starts as soon as the body ceases to be alive.
Subject to environmental conditions of extreme heat or cold, the readable signs of decomposition
will become apparent 36 to 48 hours after death (EnkiVillage, 2017). These signs include
bloating of the body and a marbling discoloration of the skin in a spider web pattern along
surface blood vessels. As the body continues to decay, the skin surface will open and body fluids
will begin to seep out. In advanced stages of decomposition, the body is often no longer
identifiable by facial recognition, and DNA testing or dental records become the tools to
determine identity. At very advanced stages of decomposition, flies and maggots begin to
emerge, and the number of life cycles of the maggot-to-fly can be estimated by a forensic
entomologist to provide the amount of time that has passed since these insect life cycles began.
Once these preliminary examinations have been made, the pathologist will cut the corpse open to
conduct a detailed internal examination of each organ to look for signs of trauma, disease, or
external indicators that might explain the cause of death, such as water in lungs or toxins in
blood.
Causes of Death
There are a wide range of possible causes of death and pathologists are trained to look for these
indicators, gather the evidence, and develop an expert opinion regarding the cause of death.
Causes of death can include:
• Laceration or Stabbing
• Shooting
• Blunt force trauma
• Asphyxiation
• Toxic substances
• Electrocution
• Depriving necessities of life
In cases of laceration or stabbing, wounds are inflicted by a sharp weapon or pointed object. The
pathologist will attempt to determine if the death was caused by damaging a vital organ or by
blood loss. The distinction here is that a person may be cut or stabbed in a way that causes them
to bleed to death, which will be indicated to the pathologist by only a small amount of blood
remaining in the body. Alternately, a laceration or stab wound may penetrate the heart, lungs, or
the brain in a way that causes the organ to stop functioning and causes death. In these cases, the
pathologist will make a determination and render an opinion of fatal organ damage.
In cases of stabbing, the pathologist can sometimes illustrate the entry point of the wound and
trace the wound path to determine an angle of entry indicating how the stab wound was inflicted.
The size, depth, and width of the wound may indicate the size and type of weapon used to create
the injury. Similarly, examining the characteristics of the wound can provide information to
allow the pathologist to offer an expert opinion on the direction of a laceration or cut wound by
illustrating the start point and the termination point. This information can be helpful for
investigators in reconstructing or confirming the actual actions and weapons used in a criminal
event.
In cases of shooting, the pathologist will make a determination of whether death was caused by
the fatal destruction of a vital organ or by blood loss. Recovery of a bullet or fragments of a
bullet from inside the body can be helpful in ballistic analysis. Examining the entry wound can
sometimes indicate the distance from which the wound was inflicted. In cases of point blank or
direct contact shootings, gunshot (burned gun powder) residue will be present at the entry point
of the wound. As with stab wounds, the pathway that the bullet travelled from the entry point
into the body to where it came to rest can sometimes be identified by a pathologist to determine
the angle of entry. For investigators, this information can be helpful in reconstructing the
criminal event and determining the location of the shooter. In cases of self-inflicted gunshot
wounds, a point blank entry point and a bullet path indicating a logical weapon position in the
hand of the victim can provide some confirmation or contradiction of the self-inflicted wound
theory.
In cases of blunt force trauma, the pathologist will look for indications of organ destruction or
massive internal bleeding causing death. Blunt force trauma can be inflicted in many ways, such
as massive sudden trauma from a fall from a great height, or a high-speed car crash that can
immediately damage the brain, the heart, or the lungs to the point where they cease to function
resulting in death. Other blunt force traumas, such as a strike to the head with a weapon, may not
immediately cause death, but result in massive bleeding and internal accumulation of blood that
can cause death. In cases of head injuries pathologists will sometimes be able to determine the
contact point where the injuries were inflicted, and they will be able to point to the contre coupe
injury effect, which happens when the head is struck on one side and the brain is so traumatically
moved inside the skull that it also become damaged on the opposite side and bleeding occurs at
the top of the brain. This bleeding inside the skull can sometimes cause death.
In a similar effect, Shaken Baby Syndrome (SBS), (Elsevier, 2016) occurs when an infant child
is violently shaken by a person and the baby’s brain moves back and forth traumatically inside
the skull causing bruising and sometimes fatal bleeding at the front and back of the brain. An
examination by the pathologist for the contact points and internal bleeding can provide valuable
clues to the manner in which the blunt force trauma was inflicted. According to An Investigator’s
Manual for Shaken Baby Syndrome, studies indicate that SBS is the leading cause of death in
children under two years of age and research studies the United Kingdom and the United States
indicate that SBS may occur each year in as many as 24 to 30 per 100,000 children under two
years of age (Smith, 2010).
In cases of asphyxiation, a pathologist will look for indicators of how the body was deprived of
oxygen. Several common means include strangulation, suffocation, smoke inhalation, or
drowning. For strangulation, the pathologist will look for bruising around the neck inflicted by
choking hands or by a ligature. A ligature is any item, such as a rope or a belt, which could be
used to restrict breathing and stop oxygenated blood going to the brain, thus causing death. If a
ligature has been used and removed, it will leave a distinct abrasion line. If a dead body is found
with a ligature in place, investigators should take great care to not untie the ligature, but cut it off
of the victim, as this allows the ligature size to be measured and compared to the size of the neck
to determine the amount of breathing that was restricted. Once the ligature is removed from a
dead body, a distinct ligature mark or a groove in the flesh will sometimes be visible.
To determine strangulation, the pathologist will examine the eyes of the victim for the presence
of small ruptured blood vessel that appear as red spots on the white of the eyeball. These spots
are known as petechial hemorrhage, and will often be visible in victims of strangulation (Jaffe,
1994).
Suffocation as a cause of asphyxiation occurs when a victim’s breathing is stopped by an object,
such as a pillow or a plastic bag, which restricts the ability of a victim to breath, thus causing
death. Unlike strangulation, suffocation has fewer indicators of violent trauma. Suffocation
deaths are sometimes accidental and are harder for pathologist to conclusively determine. The
presence of a suffocation device at the scene of the death is sometimes a first clue to this cause.
Other contributing causes can be the limited ability of a victim to remove the device that
accidentally obstructs their breathing, as may be found with a very young child, a handicapped
person, or a frail elderly victim.
Another unique type of asphyxiation death is Auto Erotic Asphyxia (AEA). This occurs when a
person is attempting to enhance their sexual arousal or pleasure while masturbating and apply
self-strangulation with a ligature device. Their goal in AEA is not suicide but rather to reach a
state of extreme oxygen deprivation and euphoria at the time of orgasm. This strategy can go
wrong when the individual passes out and their ligature does not release causing continued
strangulation and death. These cases can resemble suicide; however, they are really death by
misadventure because the victim had no intent to kill themselves. AEA can sometimes be
distinguished from suicide by the existence of apparent masturbation, pornography at the scene,
and ligature devices that have releasable controls.
In cases where asphyxiation is caused by smoke inhalation, a pathologist can find signs of soot
blackening in the lungs and, if the air containing the smoke was sufficiently hot, the lungs will
also show signs of burn trauma. Because arson is sometimes used as a means of disguising a
homicide, finding a dead body in a burning building, and not finding signs of smoke in the lungs,
is a red flag for possible death by homicide.
In cases where asphyxiation is caused by drowning, a pathologist will find signs of water present
in the lungs. If there is a question as to the location of the drowning, it is possible to have a
diatom test conducted on the victim’s tissue. If the victim was drowned in fresh water, the
diatom material, which is microscopic algae, will have migrated from the water in the lungs to
the blood and tissue of the victim. These microscopic algae are species unique to a particular
body of water. Diatom material found in a victim’s lungs should match the diatom sample from
the water where the body was found. If it does not match, this suggests that the victim drowned
elsewhere.
In cases of toxic substances, a pathologist will test the stomach contents, the blood, eye fluid
known as vitreous humor, and tissue samples from various organs in the body for poisons, drug
overdose, the ingestion of toxic chemicals, or toxic gas inhalation. Any of these substances can
cause death if ingested or inhaled in sufficient quantities.
In cases of electrocution, a person dies because of an electrical current passing through their
body that stops the heart. A pathologist will look for signs to confirm that a current passed
through the body, including contact burns where a person has touched a source of power that
entered their body and existed to a grounding point. This grounding point is often at the ground
through the feet, but can be through a shorter contact pathway, if another hand or part of the
body was in contact with a grounded object. Burns will also be visible where the electrical
current exited the body.
Cases where the necessities of life have been deprived generally occur where there is a
dependent relationship between a caregiver and a victim. The victims in these cases are typically
very young or very elderly persons who are unable to take care of their own needs. These cases
often take place over and extended periods of time and may include other types of physical
neglect or abuse. Failing to provide necessities of life is such a significant issue that the Criminal
law in Canada makes provision for this as an offence.
Duty of persons to provide necessaries
215 (1) Everyone is under a legal duty
(a) as a parent, foster parent, guardian or head of a family, to provide necessaries of
life for a child under the age of sixteen years;
(b) to provide necessaries of life to their spouse or common-law partner; and
(c)to provide necessaries of life to a person under his charge if that person
(i)is unable, by reason of detention, age, illness, mental disorder or other cause, to
withdraw himself from that charge, and
(ii) is unable to provide himself with necessaries of life.
Marginal note: Offence
(2)Every one commits an offence who, being under a legal duty within the meaning of
subsection (1), fails without lawful excuse, the proof of which lies on him, to perform that
duty, if
(a)with respect to a duty imposed by paragraph (1)(a) or (b),
(i)the person to whom the duty is owed is in destitute or necessitous circumstances, or
(ii)the failure to perform the duty endangers the life of the person to whom the duty
is owed, or causes or is likely to cause the health of that person to be endangered
permanently; or
(b) with respect to a duty imposed by paragraph (1)(c), the failure to perform the
duty endangers the life of the person to whom the duty is owed or causes or is likely to
cause the health of that person to be injured permanently. (Justice Laws Canada, 2017)
Marginal note: Punishment
(3)Every one who commits an offence under subsection (2)
(a)is guilty of an indictable offence and liable to imprisonment for a term not exceeding
five years; or
(b) is guilty of an offence punishable on summary conviction and liable to
imprisonment for a term not exceeding eighteen months. (Justice Laws Canada, 2017)
If the death of a person is found to be the result of failing to provide the necessities of life, the
responsible caregiver can ultimately be charged with criminal negligence causing death.
