Forensic Entomology

1. Forensic Entomology Use of Insects that inhabit decomposing remains for legal investigations

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

4. What is Forensic Entomology? • Medicolegal(criminal) • Urban (criminal and civil) • “legal proceedings involving insects and related animals that affect manmade structures and other aspects of the human environment” • Stored product pests (civil) 

5. Postmortem interval (PMI) • Forensic Entomology is used to determine (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.

6. Differentiate between PMI and Time of Death • Not always equal • 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

7. Blow Flies • Most useful species to Forensic Entomologists • Usually the first to arrive • Females lay their eggs around body openings • Nose, mouth, ears, eyes, genitals, wounds

8. 5 Stages of Development • Eggs • 2mm in length, last about 1 day • Larvae • 1st instar, 5mm after 1.8 days • 2nd instar, 10mm after 2.5 days • 3rd instar, 17mm after 4-5 days • Feed on flesh • Prepupae • 3rd instar moves away from body • 12mm, seen 8-12 days after eggs deposited • Pupa • Darkens with time, looks like rat droppings • 9mm, seen 18-24 days after eggs deposited • If empty cases are seen, person has been dead about 20 days • Adult • Appear metallic green or blue

10. Beetles • Larvae of beetles very different • Larvae have 3 pairs of legs • Range from white, fat and hairless to dark brown, thin, and hairy • Many are black with plates on back • Skin beetle larvae found in later stages of insect succession • Used in museums to clean bones • Rove beetles, sexton beetles, and carrion beetles eat maggots • Sexton beetles are nocturnal and usually found under the body or in the soil

12. Cockroaches • Have strong mandibles and can produce damage to skin that resembles abrasions or chemical burns • Can consume hair • Most common species are American, Australian, and German cockroaches

13. Other Organisms • Red-tailed flesh fly • Skip egg stage • Less numbers of them, but larger in size • Bronze dump fly • Found on remains with fecal material or exposed gut • Greenbottle blow fly • Found in southern US • Larvae live in moist habitats • Hairy maggot blowfly • Larvae consume other larvae • Sometimes the only insect recovered on bodies in southeastern US

14. Circumstances of Death • Sites of infestation • Wounds • Genitoanal region – sexual crime • Toxicology evidence • Sample from maggots, empty puparia, or larval skin cast to test for chemicals

15. Collecting Entomological Evidence Written and photo documentation should always be made

16. At the Crime Scene • Habitat dictates what type of insects could be found • Estimate number and kinds of flying and crawling insects • Locations of major infestations • Insect predation • Exact position of the body • Part that are in contact with substrate • Where sunlit and shaded on the body during a day • Insect activity 3-6 m from the body • Note anything that could alter environmental effects on the body

17. Climatological Data • Insect life is determined by temperature and humidity • The following should be collected from a scene: • Ambient temperature • Ground temperature • Body surface temperature • Under body surface temperature • Maggot mass temperature • Soil temperature after the body is removed • Directly under ground cover, 4cm deep, 20 cm deep • Weather data should be collected from the nearest meteorological station

18. Collecting Specimens • Passive collection of adults using sticky traps • Insect net is used to collect flying insects • Eggs, larvae, pupa, and adults on the surface of the body should be collected and preserved • Live specimens should also be obtained and placed on rearing medium • Insects within the body should be collected at autopsy

19. Back at the Lab • Live specimens should be placed in incubators with known temperature and humidity levels • Pictures should be taken to document changes • Each species of insect should be determined • Experiments outdoors near the crime scene may be necessary for environmental conditions

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

21. Fresh • 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.

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

23. Decay • 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

24. Post-Decay • 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.

25. 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.

26. The End