Forensic Entomology

1. Forensic Entomology Critters on Cadavers

4. What do Forensic Entomologists Do? • Forensic Entomologists apply their knowledge of entomology to provide information for criminal investigations. • A forensic entomologist’s job may include: • Identification of insects at various stages of their life cycle, such as eggs, larva, and adults. • Collection and preservation of insects as evidence. • Determining an estimate for the postmortem interval or PMI (the time between death and the discovery of the body) using factors such as insect evidence, weather conditions, location and condition of the body, etc. • Testifying in court to explain insect-related evidence found at a crime scene. Cool Jobs: Forensic Entomology Discovery Video Did you know? Maggots can be used to test a corpse for the presence of poisons or drugs. Some drugs can speed up or slow down the insect’s development

5. Insects as Evidence • Most insects used in investigations are in two major orders: 1 – Flies (Diptera) and 2 – Beetles (Coleoptera) • Species succession may also provide clues for investigators. Some species may to feed on a fresh corpse, while another species may prefer to feed on one that has been dead for two weeks. Investigators will also find other insect species that prey on the insects feeding on the corpse.

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

7. 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

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

9. 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

10. 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

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

13. Insects as Evidence • Weather data is also an important tool in analyzing insect evidence from a corpse. Investigators will make note of the temperature of the air, ground surface, the interface area between the body and the ground, and the soil under the body as well as the temperature inside any maggot masses. They will also collect weather data related to daily temperature (highs/lows) and precipitation for a period of time before the body was discovered to the time the insect evidence was collected. • Other factors that might affect their PMI estimates: • Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs? • Were other insect species present that may have affected the development of the collected species? • Were there drugs or other poisons in or on the body that might have • affected the larvae’s development? • Did you know… The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate. Click the image to view a video about the Body Farm!

14. 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

15. 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

16. 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

17. Phylum Arthropoda • Not as large of a biomass as bacteria – but run a respectable second! • Unifying Characteristic – hard exoskeleton • Class Insecta includes bees and wasps (Order Hymenoptera,) flies (O. Diptera,) butterflies (O. Lepidoptera,) dragonflies (O. Odanata,) beetles (O. Coleoptera,) etc. • “True Bugs” are Order Hemiptora. No hemiptorans have any consequence for forensic science – so erase “bugs” from your vocabulary!

18. 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.

19. PMI Conditions PMI must take into consideration many environmental variables • Temperature • Time of day death occurred • Time of year death occurred • Whether the corpse is submerged in soil or water.

20. After Death • As the body decays, odors attract insects to the dead body. Levels ofputricine (decomp. enzyme,) sulfur and methane compounds send up an “open for dinner” flare. • The flies (order Diptera) are the first to arrive. Blowflies (F. Calliphoridae) and flesh flies (F. Sarcophagidae) are flesh feeders and will be the first in line. • Flies can arrive within minutes or up to a couple hours after death. • In many cases flies arrive before the completion of a crime and are a silent witnesses.

21. Fly Life Cycle • If no trauma is present on the body, female blowflies will lay eggs in exposed body openings (ears, nose, mouth, anus, genitalia.) • Flesh flies don’t lay eggs, they deposit larvae. • The colonization pattern is due to the mouth parts of adult flies. • Blowflies and flesh flies have spongy mouth parts. They lack piercing apparatus that can cut through unbroken human skin. The body openings provide a moist, warm environment for larvae development.

22. Blowflies Blowfly Classification Kingdom: Animalia Phylum: Arthropoda Subphylum: Uniramia Class: Insecta Order: Diptera Family: Calliphoridae

23. Blowfly Eggs • Small, 2-3 mm length, elongate, whitish to yellowish • Found in large clusters in and around body openings as well as injuries • Clearly visible to naked eye • Colder months may see fewer in numbers • Can be found in more hidden locations such as under eyelids or in nostrils • Eggs typically hatch within hours but may take up to 2-3 days depending on conditions

24. Blowfly Larvae • One fairly small and featureless larvae hatches from each egg • The body tapers from anterior to posterior – Mouth at the anterior, spiracles at the posterior • Posterior contains breathing apparatus called spiracles • Spiracles, along with body size and shape provide important info for identification

25. Blowfly larvae • Large numbers of blowfly typically hatch at a time and remain together while they feed on a corpse • These maggot masses generally form in the head region and move down the torso as they feed. • As they feed the larvae secrete digestive enzymes which allows them to consume nearly all the soft tissue on the corpse

26. Blowfly life cycle • Blowfly larvae go through three instars (molts) • They are considered fully grown at the third instar • This can occur in several days or several weeks depending on species, environmental conditions and number of larvae present

27. Pupa Stage • After the 3rd instar larvae go through a drastic behavioral change • they crawl away from the corpse and burrow down into the soil to transform into the pupal stage and complete the life cycle

28. Pupa • The pupa form when the outer larval skin hardens and shrinks • Inside this “case” the adult blowfly will form • Once the adult fly emerges, the pupal case does not decompose. It can remain under a corpse for hundreds of years • Pupal cases can provide valuable forensic info to investigators long after a crime has been committed.

30. Blow Fly Metamorphosis Adult • 1st – Adult flies lay eggs on the carcass especially 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 12-24 hours. • 3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages. • 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 4-5 days • 4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil. • 5th – Adult flies emerge from pupa cases after 6-8 days. pupa eggs 1st instar larva 3rd instar larva 2nd instar larva It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body.

31. Postmortem Interval (PMI) • Entomological evidence collection can be done in a variety of ways: • Identify the species • Document larvae length • Determine the instar • Determine postmortem interval estimation • Depending on species- extrapolation of instar length or the accumulated degree day theory

32. Post Mortem Intervals • PMI – The use of insect life cycles to estimate the time a corpse has been in the location where it was found • PMI does not DETERMINE the time of death • Time of death is established by the medical examiner • Forensic entomology can provide value information for the M.E.

33. 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

34. Examples of Diptera (Flies) • Early Stage Decomposition Blow & Greenbottle Flies(Calliphoridae) Metallic thorax and abdomen Life Cycle of a Calliphoridae Fly • Late Stage Decomposition Flesh Fly (Sarcophagidae) Striped thorax House Fly (Muscidae) Cheese Skipper (Piophilidae)

35. F.E. Applications • Time of injury vs. death • Estimation of time of death • Whether or not a corpse has been moved • Instances of insects as weapons • Child and elderly abuse and neglect • Single vehicle car accidents (insect stings and path vehicles have traveled) • Aircraft crashes (instrument obstruction and engine and fuel line clogging)

36. Insects and Illegal Drugs • Shipments of illegal drugs often contain insect infestations, especially cannabis and heroine (derived from poppy plants.) • Analysis of insect “stowaways” can allow investigators to track country of origin, and in many cases the local area of cultivation. • PMI used to detect illegal drugs/poisons in fly larvae (consumed from corpses)

37. The morale of the story… • Insects are becoming invaluable in the investigation of crime • Forensic entomology is one of the fastest growing specialties in forensic science. • All Crime Scene Investigation Units MUST be prepared to include insect collection, identification and analysis in their investigations.