Chapter 9: Injury and Death Investigations
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Chapter 9
Injury and Death Investigations
Objectives
1. Understand the various legal definitions related to felony assaults and homicides.
2. Discuss the various stages of the medico-legal examination, including the autopsy.
3. Describe the various postmortem changes occurring at the time of death.
4. Recognize the potential evidentiary value of gunshot wounds, incised and stab wounds,
lacerations, and defensive wounds.
5. Discuss the role of the forensic entomologist in determining time of death.
6. Identify the characteristics of strangulation wounds.
Introduction
The investigation of felonious injuries and criminal homicides is one of the most important, yet
difficult, responsibilities assigned to an investigator. First, these crimes are among the most
serious offenses in society, both in terms of the severity of harm and penalties associated with
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For these cases in particular, investigators may need to call on the assistance of experts in the
scientific and medical fields. Investigators should create working relationships with specialists
Lecture Notes
I. The Law
State statutes contain different names for felonious assault—such as aggravated assault, assault
with intent to commit murder, and felonious battery—but all have one common legal element,
namely, that the assault was committed for the purpose of inflicting severe bodily harm or death.
In most such assaults, a deadly weapon is employed.
Murder is one type of homicide, which is divided into two broad classifications: nonfelonious
Felonious homicides are treated and punished as crimes and typically fall into two categories:
murder and manslaughter. Murder is defined in common law as the killing of any human being
II. The Medico-Legal Examination
The medico-legal examination brings medical skill to bear on injury and death investigations.
The medical specialist frequently called on to assist in such cases is the forensic pathologist.
Forensic pathology, a subspecialty of pathology, is the study of how and why people die.
III. The Autopsy
All violent and suspicious deaths require an autopsy to determine the time and precise cause of
death. The autopsy may also answer the following questions:
• What type of weapon was employed?
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• If multiple wounds were inflicted, which wound was fatal?
• How long did the victim live after the injury?
Answers to all or even some of these questions increase the possibility of bringing the death
investigation to a successful conclusion.
A. Dead Body Evidence Checklist
The following dead body evidence checklist will assist both the investigator and the medical
examiner in systematically following all the steps necessary to be certain no physical evidence
is overlooked:
• Thoroughly photograph everything before moving or touching it.
• Collect fragile evidence on the body.
• Obtain samples of hair, fingernails, and other trace evidence.
• Brush the head hair and the pubic region (if the body is unclothed). Hold butcher paper
under the area being brushed.
IV. Postmortem Changes and Time of Death
A recurring problem in forensic pathology is determining the time of death within the limits of
probability. It is necessary to be alert to the possibility that the postmortem interval (the time
elapsed from death until discovery and medical examination of the body) may be preceded by a
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A. Estimating Time of Death
Many physico-chemical changes begin to take place in the body immediately or shortly after
death and progress in a fairly orderly fashion until the body is fully decomposed. Each change
B. Algor Mortis (Body Cooling)
After death, the body cools from its normal internal temperature of 98.6°F to the surrounding
environmental temperature. Many studies have examined this decrease in body temperature,
C. Ocular Changes
In ocular change, the cornea becomes cloudy within 2 hours or less if the deceased dies with
D. Stomach Contents
Examination of the stomach contents may provide information not only about the time of
death but also about what the person had eaten just before dying.
E. Rigor Mortis
After death, the muscles of the body initially become flaccid. Within 1 to 3 hours they
F. Livor Mortis
Livor mortis (lividity, postmortem hypostasis) is a reddish purple coloration in dependent
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areas of the body due to accumulation of blood in the small vessels of the dependent areas
G. Cadaveric Spasm
Cadaveric spasm refers to a kind of instant rigor mortis. The same physiological changes
occur except at a more accelerated rate. Cadaveric spasm is also commonly called “a death
H. Decomposition
The different rates and types of decomposition a body undergoes depend on the environment.
V. Forensic Entomology
Forensic entomology is the study of the insects associated with a dead body, which is typically
used to determine the elapsed time since death. An analysis of the insects found on a homicide
VI. Evidence from Wounds
A. Firearm Wounds
When a bullet strikes a body, the skin is first pushed in and then perforated while in the
stretched state. After the bullet has passed, the skin partially returns to its original position and
the entry opening is drawn together and is thus smaller than the diameter of the bullet. In
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It is very important to be able to estimate the distance from which a shot was fired. In
practice, a distinction is made among contact, close, and distant shots. A contact bullet
wound is made when the muzzle of the weapon is pressed against the body when the shot is
fired. A close shot produces a zone of blackening around the entrance wound of the track,
either on the skin or on the clothes. The difference in the size of the wounds and damage done
between handgun bullets and rifle bullets, especially those of a large caliber, can be
considerable.
Detecting firearm residues on the hands of an individual may be of great importance in
evaluating deaths caused by gunshot wounds. One of the earliest methods of determining
whether an individual discharged a weapon, the paraffin test or dermal nitrate test, was based
on the detection of nitrates on the surfaces of the hands. This test is no longer considered valid
because no distinction can be made between nitrates of gunpowder origin and those from
other sources, which are quite commonly encountered in day-to-day living.
B. Incised and Stab Wounds
The incised wound—more commonly referred to as a “cutting wound”—is inflicted with a
sharp-edged instrument such as a knife or a razor. Most frequently, death is caused after a stab
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C. Puncture Wounds
At one time the weapon most frequently used in assaults resulting in puncture wounds was
D. Lacerations
When used in an assault, clubs, pipes, pistols, or other such blunt objects can produce open,
E. Defense Wounds
Defense wounds are suffered by victims attempting to protect themselves from an assault,
often by a knife or club. In the most aggravated form defense wounds resulting from a knife
may even result in one or more fingers being severed.
F. Strangulation Wounds
In ligature strangulation, the pressure on the neck is applied by a constricting band that is
tightened by a force other than the body weight. Virtually all cases of ligature strangulation
VII. Suicide
For the investigator, a major concern in an apparent suicide case is to make certain that the death
was self-induced and not the result of a criminal homicide. In other cases, important information
about the victim’s behavior before death can be obtained from relatives, friends, coworkers, and
employers.
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A. Methods and Evidence of Suicide
Nine methods are most commonly employed in suicides: shooting, hanging, ingesting
sleeping pills and other pharmaceuticals, drowning, cutting and piercing, ingesting of poisons,
inhaling gases, jumping from high places, and intentionally crashing an automobile.
Certain misconceptions associated with suicidal hangings can lead to erroneous conclusions.
Occasionally, hangings are accidental, not suicidal.
Sleeping pills and other pharmaceuticals have for many years been a common means of
committing suicide. However, some deaths resulting from the ingestion of sleeping pills or
tranquilizing drugs may be accidental, not suicidal.
The ingestion of liquid poisons is sometimes clear from outward signs on the body. Many
poisons produce symptoms similar to those of certain diseases, a fact that can complicate
determination of whether a crime has been committed. A toxicologist is a scientist trained in
the identification and recognition of poisons, along with their physiological effects on humans
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Drugs are classified into different groups based on their origins and effects on the human
body. The opiate class of narcotics, which includes morphine, heroin, and oxycodone, are
The gas most frequently involved in medico-legal investigations is carbon monoxide. When a
death does result from this gas, it is generally accidental or suicidal.
The major question to be answered in death resulting from jumping is whether the victim
voluntarily leaped or was thrown or pushed. Often, there are suicide notes, witnesses who can
B. Gender Differences in Suicidal Behavior
Studies of suicide in the United States indicate that the suicide rate is higher for men than for
women, whereas the attempted suicide rate is higher for women than men. Some evidence
VIII. Fire Deaths
Frequently, human remains are found at the scene of a fire. Properly examined, these remains
may provide important data to the investigator about the facts surrounding the fire and the cause
of death.
A. Coordination and Cooperation
Coordination of, and cooperation between, police and fire investigators are of paramount
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scene, cooperation between medical personnel (preferably forensic pathologists) and
B. Degrees of Burning
Burns are medically classified into four types. The extent of burns may provide information
C. Identification of Remains
Because fire destroys human tissue, identification of the remains may be especially difficult.
The six means that follow should be considered in sequence, from the “best” identification
tools to the “worst”:
• Fingerprints
D. Scene Considerations
As with any physical evidence, burned bodies must be sketched, measured, and photographed
E. Examination of the External Body
The body of the deceased should be examined in detail both at the scene and again at the
morgue. Significant areas for examination include those discussed next.
F. Signs of Trauma
Any sign of injury to the external body should be carefully noted, sketched, and
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Another factor that may be misconstrued is the discovery that the victim’s skull is fractured.
Care must be taken to determine whether the fracture is implosive or explosive.
The inexperienced investigator may be somewhat apprehensive in attempting to evaluate the
effects of heat and flame on the skin of the victim. The formation of blisters (vesicles) is part
G. Examination of the Internal Body
After the body has been closely examined, sketched, and photographed, an internal
examination of it should be conducted by a forensic pathologist. Significant areas for
examination are as follows.
• Soot, other debris, or burning in the air passages: These findings may indicate that the
decedent was breathing while the fire was burning.
• Pulmonary edema: Frothy substance in the lungs may result from irritants breathed in
during a fire.
• Alcohol: Alcohol in blood indicates whether the decedent was incapacitated at the time
of the fire and thus unable to escape.
• Other drugs: Indications of other possibly incapacitating drugs may provide new leads.
• Carboxyhemoglobin: Carbon monoxide (CO) is an odorless, colorless gas present at
hazardous levels in all structural fires.
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at the time of the fire.
H. Motives in Fire Deaths
In fire deaths, the following motives should be kept in mind by investigators:
• Destruction or mutilation of the body to conceal the identity of the decedent.
IX. Spree Killings
The spree killer is an individual who embarks on a murderous rampage. The killer is in the grip
of strong emotions and attacks people indiscriminately. Spree killing has some similarities to
X. Mass Murders
Mass murder consists of the intentional killing of four or more people. Contrary to random
XI. Serial Murder
In the past 30 years, multiple definitions of serial murder have been used by law enforcement,
clinicians, academicians, and researchers. The U.S. Protection for Children from Sexual Predator
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A. Serial Murderers
Serial murder is a relatively rare event, estimated to constitute less than 1% of all murders
B. Myths and Misconceptions about Serial Killers
The relative rarity of serial murder combined with inaccurate, anecdotal information and
fictional portrayals of serial killers led to the following myths and misconceptions about serial
murder:
• Serial killers are all dysfunctional loners.
• Serial killers are all white males.
C. Risk Factors for Serial Murder
The behavior a person engages in is influenced by life experiences, socialization, and certain
biological, developmental, and psychological factors. Serial murderers, like all human beings,
are also a product of these factors. While the research on serial killers is limited, given the
There is no single identifiable cause or factor that leads to the development of a serial killer.
Rather, there are a multitude of factors that increase the risk of a person engaging in these
crimes.
D. Serial Murder and the NCAVC
Because many serial murderers cover many miles in a short period of time, the FBI has
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developed the National Center for the Analysis of Violent Crime (NCAVC). It is designed
E. ViCAP Crime Report
When a violent crime remains unsolved for a period of time, the local law enforcement