THE PROCESS OF DEATH AND FORENSIC ENTOMOLOGY

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

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

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

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

Livor Mortis

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

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

Stages of Decomposition

1. Autolysis2. Putrefaction 3. Black putrefaction4. Butyric

fermentation5. Diagenesis

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

Putrefaction

• 4-10 days

• Soft tissues are destroyed by bacteria

• Bacteria give off gases - bloating

• Greenish skin

• Horrible smells

12

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

14

Butyric Fermentation

• 20-50 days

• Cadaver is drying out

• Some flesh remains

• Butyric acid – cheesy odor

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

17

Saponification - “soap making”

Diagenesis

• 50-365 days• Dry decay• May mummify• Bone is altered

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

Taxonomy

• Classification system• Carolus Linnaeus (1707-1778)

• Kingdom• Phylum• Class • Order• Family • Genus • Species

Palmetto Bug

• Kingdom Animalia

• Phylum Arthropoda

• Class Insecta

• Order Blattodea

• Family Blattidae

• Genus Eurycotis

• Species Eurycotis floridana

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

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

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)

Hister beetle

Red-legged Ham beetle

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

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)