Section 5 Forensics (death)

Relationship between algor mortis and time of death?

- How fast a corpse loses heat has been measured, and investigators can determine how long ago death occurred by its temperature. - Approximately one hour after death, the body cools at a rate of 0.78°C (1.4°F) per hour. After the first 12 hours, the body loses about 0.39°C (0.7°F) per hour until the body reaches the same temperature as the surroundings

How does Illness affect rigor mortis?

- If a person dies with a fever, the body temperature will be higher, and rigor mortis will set in faster. - If a person experiences hypothermia, the onset of rigor will be slower

How does physical activity affect rigor mortis?

- If a person was exercising or struggling before death, then rigor will progress faster. Why? Bc exercise increases body temperature and decreases oxygen availability to the cells in the body and increases lactic acid levels

How does surrounding temperature affect algor mortis?

- In cooler environments, the body will lose heat faster than in hotter environments. - If it is windy, heat loss will occur faster.

How long does it take for food to be digested?

- In general, it takes four to six hours for the stomach to empty its contents into the small intestine and another 12 hours for the food to leave the small intestine - It takes approximately 24 hours from when a meal was eaten until all undigested food is released from the large intestines

How to use insects to determine time of death?

- Insects collected at the crime scene and then raised in the laboratory under the same environmental conditions as those found at the crime scene. This process can provide a more accurate estimate of time of death 1. Immediately preserve some insects from the crime scene so you know exactly how old they are at the time of discovery of the body. 2. At the crime lab, raise some of the insects from the crime scene in the same conditions as those found at the crime scene. 3. Record the length of time for development under the specific conditions found at the crime scene. 4. Compare the insects raised at the crime lab to those found at the crime scene.

How does env affect rate of decomposition?

- Moist environments rich in oxygen speed up decomposition. - Bodies decompose most quickly in air and slower in water or if buried.

What else affects livor morits?

- The extent of livor mortis is also affected by anything impeding the flow of blood, such as tight wristwatches or belts. - position the person is in affects where the blood pools (gravity)

Why does rigor mortis occur?

- The stiffness occurs because the skeletal muscles are unable to relax and remain contracted and hard - After death without circulation, oxygen flow to the cells ceases, and calcium accumulates in the muscle tissue. In the presence of the extra calcium, the muscle fibers remain in the contracted, rigid position - The muscles eventually begin to relax as the cells and muscle fibers begin to dissolve by autolysis.

Dual lividity

- clue that body was moved - could occur if the body was kept in one position two hours after death, and then moved to a second position before the lividity became permanent

What kinds of bugs are attracted to decomposing bodies?

- eggs will hatch and feed on the nutritious decomposing tissues - Blowflies (attracted first) are attracted to two gases of decomposition, putrescine and cadaverene - Tiny wasps come to lay their eggs on maggots already present on the body. Wasp larvae live as parasites inside the maggots, feeding on their flesh - The cheese skippers arrive once putrefaction is underway; they are attracted by the seepage of body fluids - Mites and beetles come last, favor dry body,tissue

Rigor mortis to determine time of death:

- starts within two hours after death. - stiffness starts in the head and gradually works its way down to the legs. - After 12 hours, the body is at its most rigid state. - The stiffness gradually disappears after 36 hours. Sometimes, depending on body weight and temperature in the area, rigor may remain for 48 hours. - If a body shows no visible rigor, it has probably been dead less than two hours or more than 48 hours. - If a body is very rigid, then the body has been dead for about 12 hours. - If the body exhibits rigor only in the face and neck, then rigor has just started, and the time of death is just over two hours. - If there is some rigor throughout the body, but a lack of rigor in the face, then the body is likely to be losing rigor, and the death occurred more than 15 hours ago.

What affects insect development?

- temperature, moisture, wind, time of day, season, exposure to the elements, and variations among individual insects - Because life cycles are affected by fluctuations in the daily environmental conditions, insects cannot provide an exact time of death, only a close estimate

ventricular fibrillation

-Disorganized, ineffective twitching of the ventricles, resulting in no blood flow and a state of cardiac arrest. -caused by electrical trauma with low voltage

questionable death

-a death that was not witnessed or that is unexpected -activates a death investigation

Dr. Charles Norris

-first appointed medical examiner for NYC -pioneer of forensic pathology

ventricular defibrillation

-high voltage current forces the heart into a state of sustained contraction -can produce electrical burns due to the high voltage

What factors affect when rigor mortis set in/how long it lasts?

1. Ambient temperature 2. A person's weight. 3. The type of clothing 4. Illness 5. Level of physical activity shortly before death 6. Sun exposure

How does sun exposure affect rigor mortis?

A body exposed to direct sunlight will be warmer, and rigor mortis would occur faster.

4 hours

About how long does it take for rigor mortis to occur?

68 F (20 C)

After a few hours, what temperature of water is enough to cause death by hypothermia?

32 F (0 C)

After a few minutes, what temperature of water is enough to cause death by hypothermia?

Can rigor mortis be used to determine time of death?

Because so many variables can affect how fast rigor mortis progresses, a precise time of death cannot be determined, it can only be estimated. However, when rigor mortis is combined with other factors, a more accurate time of death can be established

lacerations

Blunt objects produce what type of injury?

How does weight affect rigor mortis?

Body fat stores extra oxygen and will slow down rigor mortis. A person with less oxygen stored in the body experiences rigor faster

How does temperature affect rigor mortis?

Cooler body ->slower onset of rigor. warmer body -> faster onset of rigor - rxns happen faster at higher temps

Initial Decay

Corpse appears normal on the outside, but is starting to decompose from the actions of bacteria and autolysis.

Dry Decay

Corpse is almost dry. Further decay is very slow from lack of moisture.

Butyric Fermentation

Corpse is beginning to dry out. Most of the flesh is gone

legs

If a blood clot is found in the lungs, where in the body would a dissection be made to determine the origin of the clot?

urine

Opiates, diazepines, and cocaine are measured in:

lividity

Pooling of blood in the body. Provides a clue as to how long the person has been dead. Lividity first begins about two hours after death. - If death occurred between two and eight hours, lividity will be present, but if the skin is pressed, the color will disappear. After eight hours, if the skin is pressed, the lividity will remain.

blood

alcohol is measured in:

Natural death

caused by interruption and failure of body functions resulting from age or disease. most common

Accidental death

caused by unplanned events, such as a car accident or falling from a ladder

How does clothing affect rigor mortis?

clothing keeps body warm. - presence of clothes accelerates rigor mortis - naked body cools faster, which slows down the onset of rigor mortis

Autopsy

conducted to determine the manner, cause, and mechanism of death

24-36 hours

how long after death does rigor mortis go away?

larva (plural larvae)

immature form of an animal the undergoes metamorphosis (for example, a maggot)

sharp force, blunt force

mechanical trauma is divided into what two categories?

Suicide

occurs when a person purposefully kills oneself, whether by hanging, drug overdose, gunshot, or some other method

manner of death

one of four means by which someone dies (i.e., natural, accidental, suicidal, or homicidal (maybe also undetermined)

instar

one of the three larval stages of insect development

proximate cause of death

refers to an underlying cause of death, as opposed to the final cause - ex: If someone is exposed to large amounts of radiation and then develops cancer, the proximate cause of death is the radiation exposure

decomposition

rotting, of all tissues and organs. Bacteria and other microorganisms also help decompose a human body

incision wounds

sharp objects produce what type of injury?

death

the cessation, or end, of life

algor mortis

the cooling of the body after death - death heat and describes the temperature loss in a corpse - In death, the body no longer generates heat and begins to cool down.

homicide

the death of one person caused by another person

process of death

the heart stops beating, the cells of the body begin to die because they no longer receive a fresh supply of oxygen. As oxygen levels drop, the basic processes of the body fail to occur. Nerves, muscles, organs, and the brain stop working. This is the first stage of death—stoppage

cause of death

the immediate reason for a person's death (such as heart attack, kidney failure)

speed of decomposition depends on

the person's age, size of the body, environment, and the nature of death. - Sick individuals decompose faster than healthy people. - The young decompose faster than the elderly - Overweight people with rich deposits of fat and body fluids break down faster than people of normal weight. - Naked bodies decompose faster than clothed bodies. -

livor mortis

the pooling of the blood in tissues after death resulting in a reddish/purple color to the skin (death color) - process takes time (about an hr after death) -may not appear if the victim lost a lot of blood -most often occurs in lighter-skinned individuals - provides approx time of death

decomposition

the process of rotting and breaking down

mechanism of death

the specific body failure that leads to death describes the specific change in the body that brought about the cessation of life biochemical/physiological abnormality produced by cause of death that is incompatible with life ex: if the cause of death is shooting, the mechanism of death might be loss of blood, exsanguination, or it might be the cessation of brain function ex: If the cause of death is a heart attack, the mechanism of death is the heart stopping to beat or pulmonary arrest

autolysis

the spontaneous breakdown of cells as they self-digest

pupa (plural pupae)

the stage in an insect's life cycle when the larva forms a capsule around itself and changes into its adult form

rigor mortis

the stiffening of the skeletal muscles after death (death stiffness) - It is temporary and can be very useful in determining the time of death.

forensic entomology

the study of insects as they pertain to the study of legal issues

mechanical, thermal, chemical, electrical

traumatic deaths can be categorized as one of 4 categories, what are they?

asphyxiation (binds to hemoglobin better than oxygen, therefore cutting it off from the brain)

what is the mechanism of death by CO?

lack of oxygen (due to slowed breathing)

what is the mechanism of death by alcohol (and most other depressant drugs) overdose?

drowning in blood

what is the most common mechanism of death caused by blunt head trauma? (bell 148 of pdf)

poration

when current flow through tissues creates holes in the membranes of cells and can result in loss of limbs of people exposed to high-voltage circuits

injury

when determining cause of death, what takes precedence, injury or preexisting disease?

36 hours

when does livor mortis go away usually?

Stages of decomposition (within 2 days after death)

• Cell autolysis begins following death. • Green and purplish staining occurs from blood decomposition. • The skin takes on a marbled appearance. • The face becomes discolored.

Stages of decomposition (w/in 6-10 days)

• The corpse bloats with carbon dioxide as bacteria continue to feed on tissues. Eventually, the gas causes the chest and abdominal cavities to burst and collapse. • Fluids begin to leak from the body openings as cell membranes rupture. • Eyeballs and other tissues liquefy. • The skin sloughs off

Stages of decomposition (4 days after death)

• The skin blisters. • The abdomen swells with the gas carbon dioxide that is released by bacteria living in the intestines

How does temperature affect rate of decomposition?

- Bodies decompose fastest in the 21-37°C (70-99°F) temperature range. - Higher temperatures tend to dry out corpses, preserving them. - Lower temperatures tend to prevent bacterial growth and slow down decomposition.

Changes in eye following death

- Following death, the surface of the eye dries out. - A thin film is observed within two to three hours if the eyes were open at death and within 24 hours if the eyes were covered at death. -Following death, potassium accumulates inside the vitreous humor. Because decomposition progresses at a predictable rate, the buildup of potassium may be used to estimate the time of death. (method not used yet)

How can blowflies be used to determine time of death?

1. If a corpse contains blowfly eggs, then the approximate time of death would be 24 hours or less. 2. If a corpse contains third-stage larvae, then the time of death is approximately four to five days. 3. If a corpse contains pupae, then the time of death would be approximately 18 to 24 days. (larger table pg 319)

How can stomach contents help determine time of death?

1. If undigested stomach contents are present, then death occurred zero to two hours after the last meal. 2. If the stomach is empty but food is found in the small intestine, then death occurred at least four to six hours after a meal 3. If the small intestine is empty and wastes are found in the large intestine, then death probably occurred 12 or more hours after a meal.

Blowfly larvae slits

First-stage larva has one V-shaped slit (1.8 days old); second-stage larva has two slits (2.5 days old); third-stage larva has three slits (4 to 5 days old)

1.5

In the first 8 hours after death, the body temperature goes down about how many degrees an hour?

Putrefaction

Odor of decaying flesh is present and the corpse appears swollen.

Relationship between temperature and lividity

The ambient temperature at which a person dies impacts the time it takes for lividity in set in. If the corpse is left outside on a hot, summer day, livor mortis takes place at a faster rate. If the body is left in a cool room, livor mortis is slower.

What else affects algor mortis?

The excess body fat and the presence of clothing will slow down heat loss

pinky side of the forearm

Where are defense wounds typically seen?

diatoms, bone marrow

The presence of what organism present in what part of the body can help confirm death by drowning?

cause of death

The reason someone dies. - ex: Disease, physical injury, stroke, and heart attack - ex death caused by homicide: bludgeoning, shooting, burning, drowning, strangulation, hanging, and suffocation

How can algor mortis determine time of death?

Time of death determined by body temperature calculations is always expressed as a range of time because it cannot be calculated exactly; however, a rule of thumb is to expect a heat loss of approximately 1 degree F per hour.

1-2 percent

To determine whether a person died in a fire or was dead before the fire was lit, how much CO would be present in their blood if they had died before the fire?

How is the temperature of a corpse measured (algor mortis)?

To take a corpse's temperature, forensic investigators insert a thermometer into the liver

Black Putrefaction

Very strong odor. Parts of the flesh appear black. Gases escape and the corpse collapses.