Forensic science chap 5

Explain the Importance of Finding a Corpse in a Crime

Finding the corpse is a critical first step in a homicide investigation because of:

• Victim Identification: It allows for the formal identification of the victim, which is essential for linking the crime to potential suspects.

• Primary Evidence Source: The body itself is a treasure of forensic evidence. It holds the key to determining the cause, mechanism, and manner of death, estimating the time of death, and collecting biological evidence (DNA, blood, semen) and trace evidence (fibers, hair, gunshot residue).

what are some Traditional Search Methods for finding a missing corpse?

• Searching Downhill: It is physically easier for a offender to transport a body down a slope rather than up one.

• Variation in terrain: Investigators look for signs of digging, such as freshly turned soil, trenches, depressions, or unnatural mounds, that may come from a burial activity

• Vegetation: Digging a grave alters the soil (compaction, moisture, nutrients), which can cause different plants to grow or existing plants to die at the site of a grave.

• Trained Dogs: Specially trained dogs can detect decomposition odors and assist in the localization of human remains.

what is aerial reconnaissance?

The use of photography, drones or satellite imaging to detect soil disturbance and irregularities in the landscape that may not be apparent from the ground.

How and Why can Thermal Imaging be used to find a corpse?

• How: Thermal imaging cameras detect infrared radiation (heat). As a body decomposes, bacterial activity generates heat, creating a "hot spot" compared to the surrounding soil.

• Why: This technology allows investigators to scan large areas from the air (via drones or planes) and pinpoint potential gravesites with greater precision based on these heat signatures, which are not visible to the naked eye.

Define Cause of death, Mechanism of death, and Manner of Death

Cause of Death: The specific injury or disease that initiates the series of events ending in death; the reason the person died (ex: gunshot wound)

Mechanism of death: the specific change in the body (resulting from the cause of death) that lead the person to die (ex: exsanguination (bleeding to death))

Manner of death: the circumstances in which the cause of death occurred. It is a legal classification. The confirmation of the manner of death is the responsibility of the coroner or medical examiner. (ex: homicidal)

what are the common causes of death?

Blunt-force injury: caused by a non-sharpened object like a baseball pat or pipe. This can cause cuts or bruising on the skin. 

Sharp-force injury: occurs from weapons with sharp edges, like knives, axes or blades. This can cause a cut when the injury is longer than it is deep and a stab when the injury is deeper than its length.

Asphyxia: involves interfering with the intake of oxygen. This can be caused by carbon monoxide intoxication during a fire, strangulation, hanging. 

Gunshot wounds: this type of injury studied mostly to estimate the shooting distance between the gun and the victim

Substance abuse: most common cause of death.

Medical conditions: natural death, an illness or disease. Ex: heart attack. 

what are some examples of mechanism of death?

• exsanguination(bleeding to death)

• sepsis (infection that enters the blood stream)

• cessation of brain function

• respiratory arrest

• cardiac arrest, etc

what are the four manners of death?

• Natural: diseases, old age, continued environmental abuse (life-long drug abuse, exposure to asbestos) (Ex: heart attacks, cancers, pneumonia, strokes)

• Accidental: unpredictable and unnatural events with no intentions of causing harm on the part of the perpetrator or the victim (ex: car accidents, in-home electrocutions)

• Homicidal: non-accidental death resulting from negligent or intentional actions of another person. (ex: gunshot wound)

• Suicidal: intentional, self-inflected death. (ex: intentional drug overdose)

what is an autopsy?

a surgical procedure performed by a pathologist on a dead body to determine (from the body, organs, body fluids) the cause of death.

what are the main steps of the autopsy ?

all the steps of forensic autopsy must be carefully documented and photographed.

1. Physical Evidence Recovery: The body is examined for trace evidence. Hands are bagged at the scene in cases of fight or shooting to prevent contamination and loss of evidence. Items must be collected and sent to the lab:

   • Victim's clothing

   • Fingernail scrapings

   • Hair combings

   • Buccal (cheek) swab for DNA

   • Bullets recovered from the body

   • Hand swabs for gunshot residue

   • Organs and tissues for pathological and toxicological analysis.

2. External Examination: General characteristics of the body should be noted(sex, height, weight, age). All injuries, tattoos, scars, and marks are described. Special attention is given to eyes, mouth, nose, and ears (e.g., looking for petechiae in the eyelids bc it could indicate strangulation) (mouth/nose examined for the presence of traces of vomit/blood and other trace evidence). Fingerprints are taken.

3. Internal Examination: A Y-shaped incision is made (beginning at the top of each shoulder and extending down to the pubic bone), and all internal organs are removed, weighed, and dissected to find internal injuries, preexisting conditions or malformations in the organs that might have contributed to the death of the victim. Attention given to the digestive tract if poisoning is suspected or if TOD needs to be determined. Stomach can show partially digested or dissolved pills/food. 

Toxicological specimens are taken during internal examinations. Samples of blood, stomach contents, bile, and urine are taken to test for drugs, poisons, or alcohol.

Explain what algor, rigor and livor mortis are.

Algor Mortis: The cooling of the human body after death to match the surrounding environmental temperature.

Rigor Mortis: The stiffening of muscles due to chemical changes.

Livor Mortis (Lividity): The purplish-red skin discoloration that occurs after death when blood settles in the lowest parts of the body due to gravity, as the heart is no longer pumping blood.

For algor, rigor and livor mortis, explain how they can be used to determine the TOD

Algor Mortis; determination can be performed by inserting a thermometer into the liver or rectum. At an average temperature of around 20°C, the body loses heat at a rate of about 0.75°C per hour for the first 12 hours and then 0.4°C each hour until the body reaches ambient room temp. So, a warm body suggests a recent death; a body at ambient temperature has been dead for longer.

Rigor mortis; evolves over the first 24-36 hours. Begins to set in 1-2 hours after death and full rigor can be seen after 8-12 hours. First detectable in facial and neck muscles, then moves from head to toe. W time the rigifity decreases and eventually disappears in the same order it started. Reverting rigor mortis takes 24-48 hours. So, 

• No rigor, body flaccid: Death occurred less than 2 hours ago.

• Rigor present, body stiff: Death occurred more than 2 hours ago. If the body is found in a position that defies gravity, it is an indicator that death occured more than 2 hours ago, but less than 36 hours.

• Rigor disappearing, body becoming flaccid: Death occurred more than 36 hours ago or less than 2 hours ago.

Livor mortis; begins 20 min to 3 hours after death and becomes noticeable approximately 2 hours after death. Discoloration can continue for up to 8 hours, at this point the lividity is fixed and becomes permanent. Before being fixed, pressing the skin is going to remove the coloration. So, 

• Blanching: If the discoloration disappears when pressed, death occurred less than 8 hours ago.

• Fixed: If the discoloration does not blanch, lividity is fixed, and death occurred more than 8 hours ago.

• Mismatched Pattern: If the lividity pattern does not match the body's position, the body was moved after death but before lividity fixed (within ~8 hours). 

what factors influence the rate of heat loss in algor mortis?

• body surface area relative to mass (thin bodies lose heat faster

• body position (curled-up body holds on the heat longer)

• clothing on body (clothes help reduce heat loss)

• colder environment (heat loss is faster)

• submerged bodies (warmer water than the body temp will slow heat loss