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Forensic Science: Fundamentals & Investigations, Chapter 1 1
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All rights Reserved South-Western / Cengage Learning © 2009
Forensic Science: Fundamentals & Investigations, Chapter 11 2
Vocabulary
l Algor Mortis: the cooling of a body after death l Autolysis: the spontaneous breakdown of cells
as they self-digest l Cause of Death: The disease or injury that
initiates a chain of events, brief or prolonged, which produces a fatal outcome. (Add to notes)
l Death: the cessation, or end, of life
Forensic Science: Fundamentals & Investigations, Chapter 11 3
Vocabulary
l Decomposition: the process of rotting and breaking down
l Instar: one of the three larval stages of insect development
l Larva (plural is larvae): immature form of an animal that undergoes metamorposis (e.g., maggots)
Forensic Science: Fundamentals & Investigations, Chapter 11 4
Vocabulary
l Livor mortis: the pooling of the blood in tissues after death resulting in a reddish color to the skin
l Manner of death: one of four means by which someone dies (e.g., natural, accidental, suicidal or homicidal)
Forensic Science: Fundamentals & Investigations, Chapter 11 5
Vocabulary
l Mechanism of death: the specific body failure that leads to death (e.g. sepsis, respiratory depression, cardiac dysrhythmia, etc.
l Pupa (plural is pupae): the stage in an insect’s life cycle when the larva forms a capsule around itself and changes into its adult form
l Rigor mortis: the stiffening of the skeletal muscles after death
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Objectives
l explain the development of livor, rigor, and algor mortis following death
l use evidence of these to estimate time of death l use evidence on stomach contents to estimate
time of death l use insect evidence to estimate time of death l explain how environmental factors can affect the
estimated time of death
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Forensic Science: Fundamentals & Investigations, Chapter 11 7
Introduction to Death
l Death is a process, not an instant event
Forensic Science: Fundamentals & Investigations, Chapter 11 8
Introduction to Death
l Medical examiners try to determine cause and time of death using many factors. – Livor mortis – Rigor mortis – Algor mortis – Intestinal and stomach contents – Presence and life stage of insects – Changes in the eye – Decomposition
Forensic Science: Fundamentals & Investigations, Chapter 11 9
Introduction to Death
l Scientists and doctors cannot come up with 1 definition for death – Cessation of life? – Cessation of blood circulation / heart activity? – Cessation of brain activity?
l This is a controversial topic…
Forensic Science: Fundamentals & Investigations, Chapter 11 10
Introduction to Death
l Death Process – Cells die due to lack of oxygen – Cells break down (autolysis)
l Enzymes & other cell contents spill out of lysosomes and peroxisomes and digest surrounding tissues
Forensic Science: Fundamentals & Investigations, Chapter 11 11
Cause, Manner & Mechanism
l Cause, Manner, and Mechanism of death
Cause, Manner & Mechanism
Mysterious Death at the Fair l In your group, read p. 308.
Forensic Science: Fundamentals & Investigations, Chapter 2 12
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Cause, Manner & Mechanism
Mysterious Death at the Fair l Manner of Death – accidental l Cause of Death – food poisoning/water contamination l Mechanism of Death – kidney failure
l Using this scenario, the video, and your vocab, come up with a group definition for each of the above terms.
Forensic Science: Fundamentals & Investigations, Chapter 2 13 Forensic Science: Fundamentals & Investigations, Chapter 11 14
The Manner of Death
l 4(5) Manners of Death 1. Natural
l Interruption and failure of body functions resulting from age or disease
2. Accidental l Unplanned events
3. Suicidal l Person purposefully kills oneself
Forensic Science: Fundamentals & Investigations, Chapter 11 15
Manner of Death
l 4(5) Manners of Death, cont.
4. Homicidal l Death of one person caused by another
5. Undetermined
Forensic Science: Fundamentals & Investigations, Chapter 11 16
It can be difficult to determine
l A man with a heart condition is attacked and dies from a heart attack. – Is the manner of death accident or homicide?
l An elderly woman dies after being kept from receiving proper health care by her son. – Is the manner of death natural or homicide? – Was it suicide or accidental?
l In the case of an overdose – Did the person overdose on accident or on purpose?
Forensic Science: Fundamentals & Investigations, Chapter 11 17
Manner of Death
l The most common manner of death is natural
Forensic Science: Fundamentals & Investigations, Chapter 11 18
Death
Cause and Mechanism of Death l The reason for the death is the cause of
the death.
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Forensic Science: Fundamentals & Investigations, Chapter 11 19
Causes of Death
l Disease l Physical injury l Stroke l Heart attack
Forensic Science: Fundamentals & Investigations, Chapter 11 20
Causes of Homicide
l Bludgeoning l Shooting l Burning l Drowning l Strangulation l Hanging l Suffocation
Forensic Science: Fundamentals & Investigations, Chapter 11 21
Mechanism of Death
l The specific change in the body that brought about the cessation of life is the mechanism of death.
l Example – Cause – Shooting – Mechanism - Loss of Blood (exsanguination),
Cessation of Brain Function l Example
– Cause - Heart Attack – Mechanism - Heart Stopping to Beat, Pulmonary
Arrest Forensic Science: Fundamentals & Investigations, Chapter 11 22
Time of Death
l Determining time of death is important. l If time of death is established, suspects…
– Can be proven innocent if they were known to be somewhere else
– Can remain suspects if they were in the vicinity
Forensic Science: Fundamentals & Investigations, Chapter 11 23
Time of Death
l Determined by: – Livor Mortis (death color) – Rigor Mortis (death stiffness) – Algor Mortis (death heat) – Stomach and Intestinal Contents – Changes of the Eye after Death – Stages of Decomposition – Insects
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Time of Death—Livor Mortis
l Roughly - the color of death l Blood seeps down through tissues and
settles into lowest part of body – Settling is called lividity – Begins TWO hours after death
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Forensic Science: Fundamentals & Investigations, Chapter 11 25
Time of Death—Livor Mortis
l Red blood cells break down, turn bluish-purple because of hemoglobin – Hemoglobin carries oxygen and gives blood red
color
Forensic Science: Fundamentals & Investigations, Chapter 11 26
Time of Death—Livor Mortis
l The discoloration that accompanies this becomes permanent after 8 hours – Will disappear between 2-8 hours
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Time of Death—Livor Mortis
l Warmth accelerates the process l What a person is wearing can also effect
– Wristwatches and belts will impede blood flow l Lividity can determine if body was moved in
the first 8 hours - dual lividity
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Time of Death—Livor Mortis
l Lividity can determine if body was moved in the first 8 hours - dual lividity
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Time of Death—Rigor Mortis
l Roughly - death stiffness l At death, skeletal muscles
cannot relax l Without oxygen, calcium
accumulates in muscles l The muscles become stiff
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Time of Death—Rigor Mortis
l Starts 2 hours after death l This starts in the head and works its way down to the
legs l At 12 hours after death, the body is at its most rigid
state.
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Forensic Science: Fundamentals & Investigations, Chapter 11 31
Time of Death—Rigor Mortis
l After about 15 hours, the muscle fibers begin to dissolve, and softening begins.
l This stiffness will have disappeared for the most part after 36 hours.
Forensic Science: Fundamentals & Investigations, Chapter 11 32
Time of Death—Rigor Mortis
l If a body has no visible signs of rigor, it probably has been dead less than 2 hours or more than 48.
l If the body exhibits rigor only in the head and neck, the time of death is just over 2 hours.
Forensic Science: Fundamentals & Investigations, Chapter 11 33
Time of Death—Rigor Mortis
Many factors affect when rigor mortis sets in and how long it lasts: – Ambient temperature
l Cooler the body slower the onset of rigor l Warmer the body onset of rigor is faster because reactions
happen faster at high temperatures
– The weight of the body l Body fat stores oxygen will slow down rigor
– The body’s clothing or lack of it l Clothes hold in heat so a clothes body will go into rigor
faster Forensic Science: Fundamentals & Investigations, Chapter 11 34
– Any illness the person had at the time of death l Dead person dies with fever - rigor happens faster l Dead person has hypothermia - rigor happens slower
– The level of physical activity at the time of death l Person was exercising or struggling rigor will happen faster
– Exercise increases body temp – Exercise decreases oxygen availability
– Sun exposure l Body exposed to direct sunlight will be warmer
Forensic Science: Fundamentals & Investigations, Chapter 11 35
Time of Death—Algor Mortis
l Roughly - Death heat l In death a body no longer generates warmth and
begins to cool down. l To find the standard temperature of a corpse, a
thermometer is inserted into the liver. l Body heat is lost at about 1 to 1.5 (F) degrees an
hour. – After the first hour to 12 hours after death the loss of
heat is 0.78ºC (1.4ºF) – After the first 12 hours 0.39ºC (0.7ºF)
Forensic Science: Fundamentals & Investigations, Chapter 11 36
l Time of death determined by temperatures calculations is expressed as a range of time.
l Outside environment determines how fast the body loses heat
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Forensic Science: Fundamentals & Investigations, Chapter 11 37
Time of Death - Stomach and Intestinal Contents
l In general, 4-6 hours for the stomach to empty contents into small intestine
l Another 12 to leave small intestine l 24 hours after meal was eaten to leave large
intestine
Forensic Science: Fundamentals & Investigations, Chapter 11 38
Time of Death—Stomach and Intestinal Contents
Give an estimate for each of these on how much time has passed since the meal was eaten: 1. Food is still present in the stomach.
l 0-2 hours after last meal 2. The stomach is empty but food is found in the small
intestine. l 4-6 hours after meal
3. The small intestine is empty but waste is present in the large intestine. l 12 or more hours after meal
Forensic Science: Fundamentals & Investigations, Chapter 11 39
Time of Death—Stages of Decomposition
l Within 2 days after death – Cell autolysis begins – Green and purplish staining occurs from blood
decomposition – Skin marbled appearance – Face discolored
Forensic Science: Fundamentals & Investigations, Chapter 11 40
Time of Death—Stages of Decomposition
l After 4 days – Skin blisters – Abdomen swells with carbon dioxide
Forensic Science: Fundamentals & Investigations, Chapter 11 41
Time of Death—Stages of Decomposition
l Within 6-20 days – Corpse bloats because bacteria feeding on
tissues – Chest and abdominal cavities burst and collapse – Fluids leak from body openings – Eyeball and tissues liquefy – Skin sloughs off
Forensic Science: Fundamentals & Investigations, Chapter 11 42
Time of Death—Stages of Decomposition
l Speed of decomposition depends on age, size of body, nature of death – Sick people decompose faster – Overweight people decompose faster – Naked bodies decompose faster – Perfect temperature - 21-37ºC (70-99ºF)
l Higher temperatures dry out body to preserve l Lower temperatures prevent bacterial growth
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Forensic Science: Fundamentals & Investigations, Chapter 11 43
l Moist environment rich in oxygen speed up decomposition
l Decompose quickly in air, slower in water or buried
Forensic Science: Fundamentals & Investigations, Chapter 11 44
Time of Death—Insects
l Besides recording data about the environment at a crime scene, a forensic entomologist collects insect evidence.
l Within minutes of a death, certain insects arrive to lay their eggs on the warm body. Blowflies are a common example.
l As a corpse progresses through the stages of decomposition, other kinds of insects arrive.
Forensic Science: Fundamentals & Investigations, Chapter 11 45
Time of Death—Insects
l Blowfly eggs can be found in the moist, warm areas of a corpse within 8 hours after death.
l They will have progressed to the 1st of their 3 larva stages (illustration of one shown above) within 20 hours.
l By the 4th or 5th day they will have progressed to the 3rd of their 3 larva stages.
Forensic Science: Fundamentals & Investigations, Chapter 11 46
Time of Death—Insects
• By the 8th or 12th day the larvae will migrate away from the corpse to a dry place.
• Becoming pupa and immobile within 18-24 days, they will change from white to dark brown.
• By the 21st-24th day the pupa cases will split open and adult blowflies (illustration of one shown above) will emerge.
Forensic Science: Fundamentals & Investigations, Chapter 11 47
Time of Death—Insects
l Because scientists know how long it takes for the various stages of development at given temperatures, forensics entomologists can determine when the insects arrived.
l Because life cycles are affected by fluctuations in the daily environmental conditions, insect evidence cannot provide an exact time of death.
l Insect evidence, nonetheless, can yield a close estimate.
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