The Meaning, Manner, Mechanism, Cause, and Time of Death

1. The Meaning, Manner, Mechanism, Cause, and Time of Death • Death: the irreversible cessation of circulation of blood; the cessation of all brain activity. • Death is not an instant event, it is a process. This makes it difficult to pinpoint the exact moment that someone dies.

2. The Manner of Death • 4 ways a person can die: • Natural death • Accidental death • Suicidal death • Homicidal death • Undetermined death

3. Cause & Mechanism of Death • Proximate COD vs. Final COD proximate is the underlying COD; if a person is exposed to radiation and then develops cancer and dies…the proximate COD is the radiation exposure, the final COD is cancer • Mechanism of Death specific change in the body that brought about the cessation of life (exsanguination, cessation of brain function, or the heart stops beating)

4. Determining Time of Death • Livor MortisMeans ‘death color’ (literal Latin translation ‘bruise of death’). As red blood cells break down, the blood pools on parts of the skin causing a discoloration. Pooling of the blood is called lividity, and it provides clues as to how long the person has been dead. Lividity first becomes visible about 2 hrs. after death; discoloration becomes permanent after 8 hrs. (coloring won’t disappear when skin is pressed)

5. Livor mortis will not be present where clothing or accessories (belts, watches) restricted blood flow. • The ambient temperature can also impact lividity. It takes place faster in hotter weather than in colder weather. • Livor mortis gives clues as to how the corpse was positioned within the first 8 hrs. after death. Forensic pathologists can determine if a corpse has been moved if the livor mortis does not match up with the location it was found in.

6. Rigor Mortis • Literally means ‘death stiffness’. It is temporary and can be useful in determining time of death. • Starts within 2 hrs. of death-begins in the head and works its way down to the legs. • After 12 hrs., the body is in its most rigid state. • Stiffness gradually disappears after 36 hrs. • Depending on body weight and ambient temperature, rigor may remain for as long as 48 hrs.

7. Factors Affecting Rigor

8. Algor Mortis • Literally means ‘death heat’ (literal Latin translation ‘chill of death’) and describes the temperature loss in a corpse. • Forensic investigators measure liver temperature in order to determine temperature of the corpse. • Approximately 1 hr. after death, the body cools at a rate of 0.78°C per hour. • After the first 12 hrs., the rate drops to 0.39°C until the corpse reaches the same temp. as its surroundings. • This is just an estimate and should not be used as the sole determination in time of death!!!

9. Stomach & Intestinal Contents • Usually takes 4-6 hours for the stomach to empty its contents into the small intestine • Another 12 hours afterwards for the contents to leave the small intestine • Approximately 24 hours from when a meal was eaten until all undigested food leaves the body

10. Changes of the Eye • The surface of the eye dries; a thin film appears within 2-3 hrs. if eyes were open at t.o.d., within 24 hrs. if eyes were closed/covered. • Potassium accumulates inside the vitreous humor (clear gel that fills space between the lens and the retina)

11. Decomposition Within 2 days after death, cell autolysis begins following death, green & purplish staining (bruising), skin looks marbled, the face becomes discolored After 4 days, the skin blisters, abdomen swells as CO2 is released by bacteria in intestine Within 6-10 days, corpse continues to bloat until chest & abdominal cavity burst & collapse

12. Most Important Environmental Factors in Corpse Decay* • Temperature • Access by insects • Depth of Burial • * Based on study of decay rates of 150 human corpses at U. of Tenn.

13. Ecological Roles of Insects in Decomposition • Necrophages – species feeding on corpse tissue; mostly true flies and beetles; age determination (larval instar) important for PMI • Omnivores – insects that feed both on the corpse and associated fauna; ants, wasps and some beetles; may alter rate of decomposition • Parasites and Predators – many beetles, true flies and wasps that attack immature flies • Incidentals – use the corpse as a resource extension; springtails, spiders, centipedes, some mites

14. Generalized Fly Life Cycle • Eggs • Approx. 2mm long. • present in clumps of up to 300 • laying to hatching takes 1 day • Larva - 1st instar • Approx. 5mm long • initially feeds on fluid exuded from the body • migrates into body • hatching to first molt takes 1 day • Larva - 2nd instar • Approx. 10mm long • moves around in maggot mass • first molt to second molt takes 1 day • Larva - 3rd instar • Approx. 17mm long • still moves in mass • second molt to pre-pupa takes 2 days

15. Generalized Fly Life Cycle cont. • Pre-pupa • Approx. 9mm long • migrates away from the corpse seeking a suitable pupation site • does not feed • transforms into pupa • pre-pupa to pupa takes 4 days • Pupa • Approx. 9mm long and light to dark brown • resides within puparium • undergoes transformation from larval body form adult fly • does not feed • pupa to emergence takes 10 days • Adult fly • mates on emergence from pupa • feeds on protein from body fluids • lays eggs on corpse • emergence to egg laying takes 2 days

16. Initial decay - 0 to 3 days after death • From the moment of death flies are attracted to bodies. • Bacteria and the body's own digestive enzymes (normally in the intestine) spread through the body, contributing to its decomposition. • Without the normal defenses of a living animal, blowflies and house flies are able to lay eggs around wounds and natural body openings (mouth, nose, eyes, anus, genitalia) and any wounds. • These eggs hatch and move into the body, often within 24 hours. The life cycle of a fly from egg to maggot to fly takes from two to three weeks. It can take considerably longer at low temperatures.

17. Flesh flies - Family Sarcophagidae

18. Blowflies - Family Calliphoridae

19. Blowfly Larvae

20. Stage 2: Putrefaction - 4 to 10 days after death • Putrefaction begins; gases produced by anaerobic bacteria; considerable bloating; seepage of fluids; • Larval activity speeds up decomposition - the smells and body fluids that begin to emanate from the body attract more blowflies, flesh flies, beetles and mites. • The later-arriving flies and beetles are predators, feeding on maggots as well as the decaying flesh. They are joined by parasitoid wasps that lay their eggs inside maggots and later, inside pupae.

21. Stage 3: Black putrefaction - 10 to 20 days after death • Abdominal wall is broken and carcass deflates • By this stage, several generations of maggots are present on the body and some have become fully grown. • They migrate from the body and bury themselves in the soil where they become pupae. • Predatory maggots are much more abundant at this stage, and the pioneer flies cease to be attracted to the corpse. • Predatory beetles lay their eggs in the corpse and their larvae then hatch out and feed on the decaying flesh. • Parasitoid wasps are much more common, laying their eggs inside maggots and pupae.

22. Hister Beetles Prey on Blowfly Larvae

23. Stage 4: Butyric fermentation - 20 to 50 days after death • All the remaining flesh is removed over this period and the body dries out. It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms. • The reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles. Beetles feed on the skin and ligaments. Many of these beetles are larvae. They hatch from eggs, laid by adults, which fed on the body in earlier stages of decay. • The cheese fly consumes any remaining moist flesh at this stage, even though it is uncommon earlier in decay.

24. Stage 5: Dry decay - 50-365 days after death • The body is now dry and decays very slowly. Eventually all the hair disappears leaving the bones only. • Animals which can feed on hair include moths, and micro-organisms like bacteria. Mites, in turn, feed on these micro-organisms. • They remain on the body as long as traces of hair remain, which depends on the amount of hair that covers the particular species. Humans and pigs have relatively little hair and this stage is short for these species.