Determining the Time of Death TOD

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Determining the Time of Death (TOD)
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Why is it important to know the time of death?

• TOD can set the time of murder
• Eliminate or suggest suspects
• Confirm or disprove alibis

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Time of Death

• Postmortem interval (PMI)-time between the death
  and the attempt to determine the TOD
• Time that the fatal injury occurred is not always
  the TOD

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Factors used in determining the TOD

• Ocular changes
• Thin film appears over the cornea of opened eye
  within minutes of death (closed eyes- hours)
• Corneal cloudiness (2-3 hours in open eyes
• and 24 hours in closed eyes)
• Tache noire-blackish discoloration develops
• No intraocular fluid after four days

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Rigor Mortis

• Postmortem rigidity due to buildup of lactic acid
  and causing myosin and actin to harden
• Immediately following death-body is flaccid,
  followed by increasing rigidity due to lack of
  ATP and buildup of lactic acid
• Adenosine Triphosphate (ATP)-energy source
  produced in respiration in mitochondria of cells

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THE BODYRigor Mortis
Temperature Stiffness
Time Since of body of body
Death

• Warm
• Warm
• Cold
• Cold

• Not stiff
• Stiff
• Stiff
• Not stiff

• Not dead more than 3 hrs
• Dead between 3 and 8 hrs
• Dead 8 to 36 hours
• Dead more than 36 hours

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ATP-Adenosine Triphosphate
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Respiration

• C6H12O6 6O2 6H2O 6CO2 36
  ATP
• Muscles need ATP for actin and myosin to interact
• Postmortem- body uses ATP, but stops making it
• ATP, actin, and myosin lock up until
  decomposition occurs
• Appears 2-4 hours after death and after 6-12
  hours, rigor mortis is complete

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Rigor Mortis

• Cadaveric spasm-instantaneous appearance of rigor
  mortis due to forceful death-ex. Drowning
• Arrector Pili contract-muscles surrounding hair
  follicle-hair is in upright position and does not
  continue to grow postmortem

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Algor Mortis

• Postmortem cooling-2-2.5 degrees F per hour for
  first hours, 1.5-2 degrees F for first 12 hours,
  and then to one degree for next 12-18 hours

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Assumptions of Algor Mortis

• Body temperature was 98.6 degrees F at TOD(may be
  hypothermic or hyperthermic)
• Body cooling is constant
• Time of assault different than time of death
• Temp changes of inner core-rectal, liver or
  brain temp change is slower, predictable
• External factors affect rate of cooling-ex. Body
  fat and external temperature

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Livor Mortis

• Postmortem hypostasis purple coloration in
  dependent (compressed) areas of the body due to
  lack of blood circulation
• Caused by accumulation of blood in vessels in
  dependent areas due to gravity
• Also called lividity

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Livor Mortis

• Evident 30-120 minutes postmortem
• 8-12 hours (24-36 hours in cooler temps)
  postmortem- maximum color or fixed livor mortis
  due to hemolysis (blood vessels break down)
• May occur antemortem (before death) in slow
  deaths
• Can congest internal organs

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Livor Mortis

• Advanced stages-skin capillaries burst and cause
  hemorrhaging leading to petechiae hemorrhage
  (purple spots on skin)
• May go unnoticed in dark-skinned individuals
• May be misinterpreted as bruising-applying
  pressure to bruise does not cause blanching (loss
  of color) while unfixed livor mortis does
• Incision into bruise shows diffuse hemorrhage
  into tissue, but livor mortis is confined to
  vessels

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Livor Mortis

• Dependent areas resting against firm surface will
  be pale due to compression of blood vessels
• Prevents accumulation of blood
• Color may be red or pink due to carbon monoxide
  (CO) poisoning
• Red coloration due to predominance of oxygenated
  hemoglobin

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Stomach Contents

• Digestion takes between ½ hour-6 hours depending
  on size and content of meal
• Affected by many factors
• Density-increase density-slower digestion
• Drugs and alcohol-alcohol slows down digestion
  and narcotics speed up digestion
• Medical Conditions-Diabetes delays digestion and
  shock causes content retention for days

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Chemical Changes in body fluids

• Potassium in vitreous humor increases from
  TOD
• (increases as decomposition increases)

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Scene Markers/Environmental Evidence

• Any factor in the environment of the deceased
  which could determine TOD
• Ex. Uncollected mail, lights on/off, sales
  receipts in deceaseds pockets, witness accounts

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Maggots and Murder
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Forensic Entomology

• Using the developmental stages of insects to
  determine TOD

Larvae
Pupae
Eggs
Adult
Adult
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Forensic Entomology

• The study of insects in relation to a
  criminal investigation.
• Insects arrive at a decomposing body in a
  particular order and then complete their life
  cycle based on the surrounding temperature.
• By collecting and studying the types of
  insects found on a body, a forensic entomologist
  can predict the time of death.
• When one biological clock stops,
  others begin.
• --Neal Haskell, reknown forensic entomologist

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Determining the Time of Death (TOD)Using
Forensic Entomology
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Stages of Decomposition

• Initial Decay-Although body shortly after death
  appears fresh from outside-bacteria in bodys
  intestine before death begin to digest intestine
  itself.
• Autolysis-bacteria exit intestine and digest
  internal organs. The body's own digestive enzymes
  spread throughout body
• Enzymes inside cells-released when cell
  dies-break down cell and connections with other
  cells
• Flies are immediately attracted to dead bodies
  Without normal defense of living animal-
  blowflies and house flies lay eggs around wounds
  and body openings
• Eggs hatch and move into body within 24 hours.
  Life cycle of a fly from egg to maggot to
  fly-2-3e weeks

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Stages of Decomposition

• 2. Putrefaction-4-10 days after death
• Putrefaction-destruction of soft tissues by of
  micro-organisms-results in catabolism of tissue
  into gases and liquids
• First visible sign-formation of sulfhaemoglobin
  in settled blood.
• Releasing fluids into body cavities-anaerobic
  respiration - produce hydrogen sulphide, methane,
  cadaverine, putrescine, butyric and propionic
  fatty acids
• Distention of gut-Gas build up from multiplying
  bacteria-internal pressure-inflates body and
  forces fluids from cells and blood vessels into
  body cavity
• Rate of decay increases-blowflies, flesh flies,
  beetles and mites
• Late-arriving insects-predators-feed on maggots
  and flesh -Maggot masses

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One day old dead pig showing signs of skin
changes and bloating.
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Stages of Decomposition

• 3. Black Putrefaction-11-20 days after death
• Bloated body collapses-creamy flesh-exposed parts
  are black in color and very strong smell of
  decay.
• Body fluids drain from body and seep into soil
• Insects consume most of the flesh and body
  temperature increases with activity.
• Bacterial decay important-bacteria consume body
  if insects are excluded
• Several generations of maggots-migrate from body
  and bury in soil to pupate
• Predatory maggots are much more abundant
• Pioneer flies cease to be attracted to corpse.
• Predatory beetles lay their eggs in the corpse
  and their larvae then hatch out and feed on flesh

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One week old pig-larva develop migrate from
body to pupate
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Butyric Fermentation

• 20-50 days after death
• Dessication of corpse-remaining flesh is removed
  and butyric acid released
• The surface of body in contact with ground
  becomes covered with mold as body ferments.
• Beetle larva and adults feed on skin and
  ligaments.
• Predators and parasitic wasps and beetles

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Dry Decay

• 50-365 days after death
• Body is dry and decays slowly-Eventually leaving
  only skeleton
• Diagenesis-process that changes skeletons
  proportions of organic (collagen) and inorganic
  components (hydroxyapatite, calcium, magnesium)

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PMI--Postmortem Interval

• PMI-amount of time b/w TOD and bodys
  discovery
• Estimation of PMI- set minimal and maximal PMI
  
• Minimal PMI -determined by estimating age of
  developing immature insects collected when corpse
  is discovered
• Maximum PMI-determined from species of
  insects present and weather conditions needed for
  the activity of these species

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Temperature

• Ambient heat plays a role during egg and
  early larval development but after that its
  effect decreases rapidly. Maggot masses generate
  their own heat.

Taking temperature of the maggot mass can find it
as high as 125 degrees F.
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Forensic Entomology

• Using developmental stages of insects to
  determine TOD

Larvae
Pupae
Eggs
Adult
Adult
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Forensic Entomology

• The study of insects in relation to a criminal
  investigation
• Insects arrive at decomposing body in a sequence
  and complete their life cycle based on
  surrounding temperature
• Forensic entomologist can predict the time of
  death

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Metamorphosis

• Complete metamorphosis (holometabolous)
  -development from egg to larva to pupa to adult
• The white crust in the picture are the fly
  eggs.

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Larva

• Larva hatch from the eggs and increase in
  size by growth steps called instars.
• Larva migrate from corpse and develop into
  an inactive pupal stage
• During this time, the adult insect develops
  internally.

Two larval instars.
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The Blowfly

• Acts as both necrophages and as predator
• One of the most common species on dead bodies
• Often arrive within 10 minutes
• Feed on blood and lays eggs in body cavities
• If food source is exhausted- will prey on other
  species in same genus (Chrysomya)

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• Maggots (fly larvae) are remarkable eating
  machines
• Posterior spiracles
• Spiracles are used for breathing-posterior
  spiracles-means that maggots can breath feed 24
  hrs a day

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First instar
Third Instar
Second instar
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• Pupal Stages of House Fly

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Types of Insect Collections

• Collection are done in three ways
• Aerial
• Hand
• Live Sampling

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Aerial Collection

• Use a net in figure 8 motion over cadaver
• Collect flies and put them in ethyl acetate
• After a few seconds-put flies into 75 ethyl
  alcohol-label date, time, case , location,
  sample type and collector.

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Live SamplingMaggot Motels

• Collect 10 to 15 live maggots of varying sizes
  into a rearing chamber
• Allow to develop into pupae and then into adults.
  

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Hand Collection

• Collect maggots with forceps
• Put in boiling water to stretch them out and fix
  them
• Put maggots into ethanol with a label containing
  date, time, case , location and collector

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First instar
Third Instar
Second instar
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Maggots can consume 60 per cent of a corpse
in less than a week. Video footage R.
MajorWindows Media (77kb)Quicktime (275kb)

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Burying Beetles
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Hister Beetle
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Forensic Flies
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