8. Forensic Entomology

8. Forensic Entomology Uses Forensic Entomology History • Determine TOD “Discovered” 13th Century China. • Identify a Suspect Homicide by farmer’s sickle. • Locardian Transfers Lined up sickles and left them outside. • Locate Victim or Evidence Flies went to the sickle that had blood on • Toxicology it. • Create Crime Scene Timeline Fly Facts • One or two species find the body shortly after death (5 min - hours). • Initial egg laying (oviposition) activity will attract other flies to deposit eggs. • Oviposition frenzy. • Different ages of eggs, larvae or puparia associated with a corpse. • Oldest specimens provide maximum TOD; Youngest specimens provide minimum TOD. • Flies neither fly nor lay eggs at night. • Flies will become active after sunrise and only if the temperature is above 50ºF. Fresh Stage - Initial Decay (0 to 3 Days) • 0 to 3 days post mortem. • Body is not yet decayed. • Appears fresh from outside. • Autolysis is taking place inside. • Bacteria break out of the intestine and start digesting the surrounding internal organs. • The body’s own digestive enzymes (normally in the intestine) spread through the body. Bloated - Putrefaction (4 to 10 Days) • Bacteria break down tissues and cells, releasing fluids into body cavities. • They often respire in the absence of oxygen (anaerobically) and produce various gases. • The build up of gas creates pressure within the body causing bloating. • Bloating forces fluids out of cells and blood vessels and into the body cavity (seepage) Decay - Black Putrefaction (10 to 20 Days) • The skin of the corpse breaks as the maggots feed allowing gases to escape and the corpse deflates. • Strong distinctive odor of death. • Maggots form large feeding masses inside and on the surface of the corpse. • Insects have completed their larval development and depart the corpse to develop as pupae in the soil. • Bloated body eventually collapses. • Flesh has creamy consistency. • Exposed parts of the body are black. • Very strong smell of decay. • Large volumes of fluids drain from the body and seep into surrounding soil. • Other insects and mites feed on this material. Maggots • Feed on body tissue. • Secrete enzymes to slice through tissue. • As numbers increase, they move through the body consuming all in its path. • Once the larvae reach their final stage/instar, they crawl away from the corpse and bury themselves in dirt. • In a house they seek dark crevices (e.g. folds in bed sheets). • Larval skins harden and shrink into pupae case. • Adults emerge 6-14 days later. Post Decay - Butyric Fermentation (20 to 50 Days) • Flies and maggots are superseded by beetles. Body dries out. • Increases number and diversity. Cheesy smell (butyric acid) • Skin and cartilage are consumed. Attracts new organisms. • Body reduced to bones, hair, and teeth. • Remaining flesh is removed. • Most insects are absent. The surface of the body In contact with the ground becomes covered in mold as the body ferments. Dry Decay (50 to 365 Days) • Only hair and bone remain. Common Blowfly Time Table The Common Blowfly • Known as the common housefly. • 3 developmental stages (instar). • Attracted to the smell of death. • Lay eggs in moist warm spaces. • Temperature influences the rate at which larvae develop. 8-14 hours to hatch from time eggs are laid. 8-14 hours to complete first instar. 2-3 days to complete 2nd instar. 7-8 days to complete 3rd instar. Total of 10-13 days between egg and pupae. Adults emerge 6-14 days later. • Send chemical signals that attract other flies. Cheese Skipper Fly Arrives no later than 1 week post Faunal Regression • Insect “parade” • Carrion beetle • Parasites that feed on body • Other insects feed on parasites • Lacks precision of “maggot reading” • Moths circle the decayed and desiccated body • Animals feed on corpse mortem. After 1 month, they pop off the corpse into the soil. Cheese Skipper Larvae mean < 34 days. Soldier Flies Show up after about 20 days. 5 instars of growth. Blow Fly Species • Blue Bottle Fly (Calliphora vicina): Cooler parts of the year • Green Bottle Fly (Phaenicia sericata): Warmest parts of the year • Green Bottle Fly (Lucila illustris): Open, brightly lit habitats • Black Blow Fly (Phormia regina): Shade Blow Fly Eggs • Small (2-3 mm), whitish yellow, somewhat elongate • Warmer months: Packed into natural body openings • Cooler months: Few, difficult to locate, more deeply recessed in cryptic locations • Typically hatch within 1-3 days (depends on species and environmental conditions) • Dissection of egg samples and analysis of the state of embryonic development can give the time since oviposition Blow Fly Maggots • 3 growth stages (instars) noted by mounts before becoming fully grown • Typically large numbers of larvae hatch together and move around the corpse as a group • Disseminate bacteria and secrete enzymes - enables them to consume nearly all soft tissue of the corpse Blowfly Maggots Investigators Must: • Get local temperature readings. • Ground surface temperature readings. • Temperature of the Maggot Mass. • Indoors will add 48-72 hours to TOD. Collection of Insect Evidence • Collect both alive and preserved specimens. • Don’t mix different species. • Freeze insects used for toxicological analysis. • Put live specimens in a breathable container. • Liver as food substance. • Place dead specimens in ethyl alcohol for Cheese Skipper Fly The Common Blowfly preservation. • Ship immediately to lab. • Provide date, time, and location. low Neal Haskell, Ph.D. • Degrees: • Doctorate, Forensic Entomology • Master of Science, Forensic Entomology • Bachelor of Science, Entomology • Saint Joseph’s College & Purdue University Dr. William Bass • Forensic Anthropologist • The Body Farm • Research to determine how bodies decay in Black Soldier Fly different situations. • Entomology research 866256906287/"https://www.pinterest.c analysis/"https://www.pbs.org/wgbh/nova/article/forensics-bloodstain-pattern-analysis/