Forensic Entomology

1. Forensic Entomology Insects in the Forensic Sciences

2. What is Forensic Entomology? • The application of insects and other arthropods to legal issues and court proceedings

3. What is it used for? • Applications • Estimation of time of death • Cases involving possible sudden death • Traffic accidents with no immediately obvious cause • Possible criminal use of insects

4. How does FE work? • Fact – insects feed on humans after death. Yup – not good news, but we are part of the cycle of life! • If insects are found on a corpse, the life stage of the insect can be used to determine time of death • This calculation is known as the POSTMORTEM INTERVAL (PMI)

5. 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.

6. Divisions of Forensic Science • Urban – Relates insects to human structures and environments • Stored Products – Insect infestations of stored food and beverages • Mediocriminal – The only division that has a criminal aspect. Relates to insects feeding on human tissue in the postmortem period.

7. 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 silent witnesses.

8. Phylum Athropoda • 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!

9. 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.

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

11. Blowfly Eggs • Small, 2-3 mm length, elongated shape, white to yellow color • 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

12. 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

13. 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

14. 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

15. 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

16. 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.

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

18. 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.

19. Forensic 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)

20. F.E. Applications – Blood Evidence • “Roach Track” Confusion • Roaches are notorious for confusing blood spatter analysis • Blood trajectory is often critical to forensic investigations • Roaches, silverfish and other household insects often travel through bloodstained areas • “Roach tracks” frequently confuse forensic investigators that are untrained in how to identify them

21. Blood Spatter Confusion – Fleas and Flies • Flies also track through blood, but “fly specks” are a far greater problem for investigators • Flies ingest blood and can leave large undigested droplets behind in previously uncontaminated areas. These droplets can enlarge a crime scene unneccessarily. • Fleas also leave behind undigested blood in their feces (commonly known as “flea dirt.”) • Flea dirt in a heavily infested dwelling can falsely suggest blood “evidence”

22. Roaches, Flies, Fleas • It is becoming more clear that household insect infestations need to be included as a variable in forensic investigations • Proper identification of household pests can save valuable time and resources for technicians and investigators • Best for juries to hear about insect “confusion” from CSI’s rather than from attorneys for the defense!

23. 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)

24. The moral 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.