Time of Death, Decomposition, & Forensic Entomology

1. Time of Death, Decomposition, & Forensic Entomology Forensic Science K. Davis Disclaimer: This presentation contains graphic photos.

2. Measuring Body Temperature - Algor Mortis • Normal Body Temperature = 98.6 ˚F (37 ˚C) • After death, the body loses heat at rate of 1.5˚F/hr until it reaches ambient temperature (T of environment). • Rate will vary based on the environment. • Body temperature should be taken rectally or from the liver to be most accurate.

3. Factors that affect algor mortis rate: • obesity • clothing • warm still air • exposure to direct sunlight • enclosed environment

4. Rigor Mortis • Refers to the stiffening and contraction of muscles caused by chemical reactions that take place in the muscle cells after death • Begins throughout body at same time, but muscles become rigid at different rates in a predictable pattern

5. Predictable Pattern of Rigor Mortis 1)  2 hours after death – stiffness detectable in the small muscles of face and neck & then it progresses down toward the toes 2) Next  8 – 12 hours– entire body stiffens 3) Next  18 hours – body remains fixed • (rigid stage of rigor mortis) 4) After the rigid stage – process reverses itself; rigidity is lost in the order that it appeared, starting with small muscles of face • After another 12 hours – muscles are relaxed again • (flaccid stage of rigor mortis) • Rigor mortis is only useful for estimating time of death during first 36-48 hours after death.

6. Things that can alter the rate of rigor mortis: • 1. victim who ran from assailant before death • 2. victims of strychnine poisoning • 3. victim of any fever producing process or heat stroke • In general, heat speeds up the process and cold slows it down. • Not always reliable to determine time of death because the rate can be altered.

7. Livor mortis • Refers to dark, purplish discoloration of portions of body • Also called lividity or postmortem hypostasis • Caused by stagnation of blood in vessels and gravity

8. Livor mortis • Usually will see lividity most wherever lowest point of body was or where body was pressed against a firm surface • Color of lividity provides clues to ME • ex. Red or pinkish discoloration reveals high levels of oxygen in blood which may be caused by carbon monoxide or cyanide poisoning or exposure to cold temperatures after death • ex. Deep purple lividity may indicate death from severe heart failure, shock or asphyxia and low levels of oxygen in blood

9. Livor mortis • Appears 30 minutes – 2 hrs after death • Reaches its maximum 8-12 hrs after death • Can change if body is moved in the first few hours, but becomes fixed after 6-8 hrs • Fixing process is gradual

10. Rate of decay • Decomposition of the body involves two distinct processes: • Autolysis • process of self-ingestion • Enzymes within the body’s cells begin a chemical breakdown of cells and tissues. • Process is hastened by heat and slowed by cold. 2) Putrefaction • Caused by bacteria that destroy body’s tissues • Bacteria mostly come from intestinal tract

11. Occurs in a predictable sequence: • After first 36 hours, abdomen takes on greenish discoloration that spreads to neck, shoulders and head • Bloating begins in face, caused by gases produced by bacteria • Skin develops blisters • Skin begins to marble • Abdomen swells. Skin and hair begin to slip from body and fingernails start to come off • Body turns greenish-black color and fluids of decomposition drain from body • As body continues to swell, tissues break open releasing gases and fluids

12. Internal organs decay in predictable manner: • Intestines decay first, followed by liver, lungs, brain then kidneys • Stomach decomposition is slower because of acids in stomach • Last, uterus or prostate

13. V. Mummification • Occurs when body desiccates (dries out) in a hot, dry environment • Low humidity inhibits bacterial growth, and thus putrefaction, while at same time sucking the moisture from tissues • Process similar to making beef-jerky • In ancient Egypt, spices and salts were rubbed on corpses to hasten the decay

14. Adipocere Formation • Occurs in very wet environments within the body’s adipose (fatty) tissues. • Fat literally turns to soap • Result is a white, greasy, waxy substance • It gives the body an unreal, mannequin-like appearance • Most often occurs in bodies found in warm, damp areas • Takes at least 3-6 months to form

15. Floaters • Bodies that die in water or are dumped into water shortly after death initially sink • Eventually they rise to surface because of gases that accumulate in body’s tissues and cavities as putrefaction occurs • Temperature of water plays a role • In general, bodies found in temperate water display • Swollen hands and face after two to three days • Separation of skin from the body after five to six days • Loss of fingernails after 8-10 days • Floating after 8-10 days in warm water and after 2-3 weeks in cold water

16. Floater

17. Eyes • After death, the corneas, or clear covering over the pupils, become cloudy and opaque • Process may take only a few hours if the eyes were open at death or up to 24 hours if the eyes were closed • Concentration of potassium within the vitreous humor (thick, jellylike substance that fills your eyeballs) increases slowly during the first few days • This process is independent of ambient temperature • Only really accurate though during first few days after death

18. Stomach Contents • After a meal, the stomach usually empties itself in approximately four to six hours, depending on type and amount of food ingested • Small intestine can also be observed to see if any food remains in it • If small intestine is empty, death probably occurred at least 24 hours after victim’s last meal • If large intestine (colon) is also empty, no food had been ingested for 48 – 72 hours before death • Extremely variable however, depending on individual and type of food

19. Entomology is the Study of Insects Images from: www.afpmb.org/military_entomology/usarmyento/files/ArmyEntomology.ppt

20. Insect Biology • Insects are the most diverse and abundant forms of life on earth. • There are over a million described species- more than 2/3 of all known organisms • There is more total biomass of insects than of humans. • Insects undergo either incomplete or complete metamorphosis (Egg to larva to pupa to insect) • Larva have a soft tubular body and look like worms. Fly species larvae are “maggots”

21. What is Forensic Entomology? • Forensic Entomology is the use of the insects and other arthropods that feed on decaying remains to aid legal investigations.  • Medicolegal (criminal) • Urban (criminal and civil) • “legal proceedings involving insects and related animals that affect man-made structures and other aspects of the human environment” • Stored product pests (civil) 

22. Medicolegal Forensic Entomology • Often focuses on violent crimes • Determination of the time (postmortem interval or PMI) or site of human death based on identification of arthropods collected from or near corpses. • Cases involving possible sudden death • Traffic accidents with no immediately obvious cause • Possible criminal misuse of insects

23. Postmortem interval (PMI) • Forensic Entomology is used to determine time since death (the time between death and corpse discovery) • This is called postmortem interval or PMI. • Other uses include • movement of the corpse • manner and cause of death • association of suspects with the death scene • detection of toxins, drugs, or even the DNA of the victim through analysis of insect larvae.

24. Forensic Entomology is Applied Biology • If it weren’t for decomposition of all living things, our world would fill up with dead bodies. • When an animal dies, female insects will be attracted to the body. They enter exposed orifices or wounds and lay eggs or larvae. • A forensic entomologist: • identifies the immature insects • determines the size and development of the insects • calculates the growth of the insects and passage through stages of the life cycle in laboratory • compares the growth against weather conditions to estimate time of oviposition

25. Blow Fly Metamorphosis Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages. Adult Adult 1st - Adult flies lay eggs on the carcass (ex. at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc. 2nd - Eggs hatch into larva (maggots) in 12-24hrs. 3rd - Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instarstages. 1st Instar - 5 mm long after 1.8 days 2nd Instar - 10 mm long after 2.5 days 3rd Instar – 14-16 mm long after 4-5days 4th - The larvae (17 mm) develop into pupa after burrowing in surrounding soil. 5th - Adult flies emerge from pupa cases after 6-12 days. Pupa Pupa Eggs Eggs 1stInstar Larva 1stInstar Larva 3rdInstar Larva 3rdInstar Larva 2ndInstar Larva 2ndInstar Larva It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body. Image: http://www.umext.maine.edu/images/FlyLife.jpg Information: http://www.kathyreichs.com/entomology.htm and http://www.forensicentomologist.org/

26. Certain circumstances can change schedule • Blowflies for example, don’t deposit eggs at night and are less plentiful during winter • Insect studies most often provide a minimum time that’s elapsed since death

27. Succession of Insects on the Corpse • Estimates of postmortem intervals based on insects present on the remains are based on: • The time required for a given species to reach a particular stage of development. • Comparisons of all insect species present on the remains at the time of examination. • Ecological succession occurs as an unexploited habitat (like a corpse) is invaded by a series of different organisms. • The first invasion is by insect species which will alter the habitat in some form by their activities. These changes make the habitat attractive to a second wave of organisms which, in turn, alter the habitat for use by yet other organisms.

28. Ecology of Decomposition • Necrophages - the first species feeding on corpse tissue. Includes rue flies (Diptera) and beetles (Coleoptera). • Omnivores - species such as ants, wasps, and some beetles that feed on both the corpse and associated maggots. Large populations of ominvores may slow the rate of corpse’s decomposition by reducing populations of necrophagous species. • Parasites and Predators - beetles, true flies and wasps that parasitize immature flies. • Incidentals – pill bugs, spiders, mites, centipedes that use the corpse as an extension of their normal habitat

29. Image: http://www.nlm.nih.gov/visibleproofs

30. Decay Rates Are Variable • Studies of decay rates of 150 human corpses at in the Anthropological Facility in Tennessee (The Body Farm) • Most important environment factors in corpse decay: • Temperature • Access by insects • Depth of burial • Other Factors • Chemical-- embalming agent, insecticides, lime, etc. • Animals disrupting the corpse

31. Time of Death can be broadly estimated up to about 36 hours Temperature Stiffness Time of death Warm Not stiff Dead less than three hours Warm Stiff Dead between 3 to 8 hours Cold Stiff Dead between 8 to 36 hours Cold Not stiff Dead in more than 36 hours

32. Differentiate between PMI and Time of Death • These may not always equate. • Post mortem interval is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin. • Closed windows • Body in box or bag • Cold temperatures • Deeper burial

33. Insect species arrive at a corpse in waves like clockwork • Calculate the heat/thermal energy (accumulated degree hour) required for each stage of the Green Bottle Fly’s life cycle. • Possibly the greatest potential source of error in using arthropod successional patterns lies in the collection of specimens. • Must only be done correctly to accurately sample the insects.

34. Image: http://www.nlm.nih.gov/visibleproofs

35. Calculating PMI from Accumulated Degree Hours (ADH)

36. Calculating ADH from Climate Data

37. Using the Data • 3928 ADH in these three days (952+1488+1488). • How many ADH of 70º are there in these 3 days? 3928/70 = 56.11 hours • 72 hours at 70º would have the insects passing to the 3rd instar. But 72 hours at colder temperatures and insects will only be at 2nd instar stage.

38. Five Stages of Decomposition Fueled by Insect Activity. • Fresh • Bloat • Decay • Post-decay • Dry (skeletal)

39. Begins at death Flies begin to arrive Temperature falls to that of the ambient temperature. Autolysis, the degradation of complex protein and carbohydrate molecules, occurs. Fresh

40. Swells due to gases produced by bacteria Temperature rise of the corpse Flies still present Bloat

41. Gases subside, decomposition fluids seep from body. Bacteria and maggots break through the skin. Large maggot masses and extreme amounts of fluid. Unpleasant odor Larvae beginning to pupate. Corpse reduced to about 20% of it’s original mass. Decay

42. Carcass reduced to hair, skin, and bones. Fly population reduced and replaced by other arthropods. Hide beetles are dominant in dry environments. Mite and predatory beetle populations increase. Post-Decay

43. Dry (Skeletal) • Does not always occur especially if corpse is in a wet region. Maggots will stay longer and hide beetles will not appear. • In wet environments the hide beetles are replaced with nabid and reduviid insects. • The corpse is reduced to at least ten percent of the original mass. • In the last stage (Skeletal Stage), only bone and hair remain.

44. Methods • This project took place at the Huntington landfill beginning on September 5, 2003. • Two different areas were chosen to deposit two pigs. • Pig 1 was laid in a sunlit area. • Pig 2 was laid in a shaded woodland area about 100 feet away at an elevation of approximately 20 feet. • Both pigs were placed in cages constructed of wood and one inch chicken wire that were staked to the ground to protect from predatory animals.

45. Methods • Prior to starting the project, great care was taken to prevent insect activity from taking place. • After they died, the pigs were individually tied in two black garbage bags, placed in feed sacks, and secured. • The pigs were kept at - 80˚C in the laboratory. • They were placed in plastic bins in order to thaw for 48 hours prior to placement at the landfill. • Closed environment was maintained until they were deposited at the site.

46. Methods • Pigs with a genetic line of a minimum of fifty percent Yorkshire. • They were 8-10 weeks old and weighed approximately 40-50 pounds. • Both died on July 11, 2003 approximately 12 hours apart. • One died a natural death and the other was culled from the litter. • Both of the carcasses were in very similar condition; there were no breaks, tears or cuts in the skin.

47. Methods • Daily observations were made at both sites throughout the day at 7am, 1pm, 7pm, and 1am. • Air, ground, and maggot mass temperatures were taken at each visit and observations were recorded. • At 7am and 7pm they also collected maggot samples for analysis and photographed the scene. • Observations were noted and samples taken for a period of nine days.

48. Methods • Using insect tweezers, the investigators collected a number of maggots and dropped the samples immediately into boiling water, to kill the bacteria in the maggots and also to straighten their bodies for easier analysis. • The maggot samples were taken from different areas of the body in which there were large numbers present.

49. Methods • The maggots were then placed into a labeled jar and preserved with 70% EtOH. • They also collected interesting arthropods for analysis. • All of the samples were labeled and stored for later analysis in the laboratory.

50. Phormiaregina Spiracles are incomplete Third-instar larvae