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THE PROCESS OF DEATH AND FORENSIC ENTOMOLOGY
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The Process of Death
• Pathologist determines time of death
• Pretty accurate if body found within first 24 hours after death using the following indicators:– Algor mortis – cooling rate of body after death– Livor mortis – pooling of blood due to gravity
after heart stops– Rigor mortis – rigidity of muscles after death
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Algor Mortis• Cooling rate of body• Starting temp = 98.6 degrees• Begins equalizing temp of environment• Glaister Equation: used between 1 and 36 hours
since death, most accurate within first 12h to determine time period since death based on body temperature
Hours since death = 98.4°F – internal body temp
1.5
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Must also consider:
• Temperature of environment
• Type and layers of clothing on body
• Wetness of clothing
• Air movement
• The greater the surface area to mass ratio – body cools faster – e.g. children, small adults
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Livor Mortis• “lividity” – discoloration; black and blue• Pooling of blood due to gravity after heart stops• Appears as purplish-red discoloration• Indicates position of body at time of death• Doesn’t occur in areas of body that are in contact
with ground or constricted by other objects• Begins within ½ h. after death and most evident
within first 12 h.• Used to determine if body has been moved after
death
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Livor Mortis
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Rigor Mortis• Upon death muscles relax, ATP breaks down and
muscles become rigid
• Smaller muscles first (face, neck, jaw)
• Occurs within few hours of death and is gone within ~30 h – then body becomes limp
• Not 100% accurate - must consider:– Environmental temp– Dehydration– Muscle condition and their use before death
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Rule of thumb in estimating time of death
Temp of body Stiffness of body
Time since death
Warm Not stiff Not dead more than 3 h
Warm Stiff Dead between 3 and 8 h
Cold Stiff Dead between 8 and 36 h
cold Not stiff Dead more than 36 h
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Stages of Decomposition
1. Autolysis2. Putrefaction 3. Black putrefaction4. Butyric
fermentation5. Diagenesis
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Autolysis• 0-4 days
• appears fresh externally, but decomposing internally
• Cells self-destruct due to no oxygen, increase in carbon dioxide, decrease in pH, and wastes accumulating
• After a few days fluid-filled blisters appear and skin sloughs off
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Putrefaction
• 4-10 days
• Soft tissues are destroyed by bacteria
• Bacteria give off gases - bloating
• Greenish skin
• Horrible smells
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Black Putrefaction
• 10-20 days
• Body is mass of fluids
• Collapses as gases escape
• Flesh creamy but exposed body parts black
• Horrible smells
• Fluids drain out of body
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Butyric Fermentation
• 20-50 days
• Cadaver is drying out
• Some flesh remains
• Butyric acid – cheesy odor
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Adipocere formation• Months to years after death
• Yellowish-white, greasy wax-like substance
• Forms as a result of the breakdown of fatty acids by a particular anaerobic bacterium
• Occurs when:– Burial in moist, alkaline soild– High body fat of corpse– Burial in a casket within a vault
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Saponification - “soap making”
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Diagenesis
• 50-365 days• Dry decay• May mummify• Bone is altered
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Rough estimate – depends on temperature, moisture, scavengers,
etc. #days to become skeletonized = 1285
avg temp °C
So if a body is left in 20C (68F) it would take about 64 days for it to become skeletonized
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Taxonomy
• Classification system• Carolus Linnaeus (1707-1778)
• Kingdom• Phylum• Class • Order• Family • Genus • Species
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Palmetto Bug
• Kingdom Animalia
• Phylum Arthropoda
• Class Insecta
• Order Blattodea
• Family Blattidae
• Genus Eurycotis
• Species Eurycotis floridana
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Three ways Entomology is used in Forensics
1. Urban entomology – affecting man and his environment (e.g. termite damage to a building)
2. Stored products entomology – insects infecting food
3. Medical Entomology – insects that inhabit human remains
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Medical Entomology
• Deals with necrophagous insects – eat carrion (carcass of dead, decaying animal)
• Dermestidae - family
• Insects determine PMI – postmortem interval – time that has elapsed since a person died
Carrion beetle
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Insects of Death
• Flies (Order Diptera)
• Beetles (Coleoptera)
• Some eat flesh, some eat other species of larvae (beetle or fly) on the flesh
• Some rural, some urban• Some shade, some sun• Some nocturnal (usually beetles)
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Hister beetle
Red-legged Ham beetle
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Other uses of insects
• Presence of wounds – if maggots found on torso rather than in mouth, nose etc.
• Place suspect at crime scene – e.g. if murder suspect had chigger bites and chiggers found to only be in that one area
• Contraband trafficking may contain insects - can determine where it came from
• Insects on front of a car may indicate where a person has been
• Presence of drugs in a body may be detected by presence of drugs in maggots
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Insect development depends on:
• Temperature• Higher temp = faster growth• Requires a certain temp range – not too hot, not
too cold• Growth rate in temp-time units = degree-days or
degree-hours. Represent amt of heating/cooling needed to go from one stage to next (e.g. egg to second instar)