Chapter 12 Forensic Entomology

1. Chapter 12Forensic Entomology

2. Case study – Bugs Don’t Lie • When did the children go missing? • When were the bodies found? • List 5 reasons for suspecting the stepfather. • Summarize the entomological evidence and explain how this lead to estimating the time of death.

3. Introduction • Forensic entomology – use of insects in legal investigations • Phylum Arthropoda – insects, spiders, scorpions, crayfish, and millipedes - invertebrates - externally segmented bodies - exoskeleton made of chitin

4. Historical Development • Fig. 12-3 p. 344 • 1st documented use of insect evidence to solve crime China in 1235

5. Insects and Forensics • Head – brain, antennae, eyes, and mouthparts • Thorax – 3 prs. of legs and possibly 2 prs of wings • Abdomen – reproductive and digestive organs • 29 orders of insects – flies and beetles most important to forensics

6. Insect Orders • Flies – Diptera • - found in almost every environment • ex) blowflies – found at 1st stages of decomposition • Lay eggs in body openings bloated stage the eggs hatch into maggots move away from body to pupate beetles move in and continue decay process

7. Insect Orders • Beetles – Coleoptera • - most prominent in later stages of decomposition • Final stage = skeletal – beetles are joined by other soil-dwelling insects • See Fig. 12-5 p. 346

8. Insects at Work • Life cycle – egg larva(feeding stage)  pupa(relatively inactive, nonfeeding stage) • Abiotic and biotic factors interact to maintain balance in an ecosystem • AF = sun, atmosphere, weather • BF = organisms or remains of organisms

9. There is strength in numbers • 1 million species of insects • Short lifespan but produce large numbers of eggs • Contribution to ecosystem = loosening of soil, pollination, consuming plant pests • Incomplete metamorphosis – nymph(wingless) molts several times adult • Meteorology vs climatology

10. Postmortem Interval(PMI) • Need to establish timeline of events • PMI is an important element of that timeline • http://www.pbs.org/wnet/nature/episodes/crime-scene-creatures/interactive-determine-the-time-of-death/4390/

11. Collecting and Preserving Entomological Evidence • Include info about rainfall and temperature • Investigation team collects evidence and sends it to the forensic entomologist at the lab • 1. Start collection several feet away from the body • 2. measure distance between insect evidence and body • 3. collect samples at all stages on, near, or under body • 4. at lab – raise samples at same conditions as crime scene

12. What to record • 1. temperature • 2. type and amount of precipitation • 3. type and amount of light • 4. humidity • 5. amount and direction of wind

13. Temperature • An increase in temperature = an increase in insect development • A)ambient - 1 and 4 feet above the body • B) soil – surface, 10 cm. below surface, and 20 cm below surface

14. More on collecting and preserving evidence • Nets for flying stage • Pinned or transferred to vial in 80%alcohol • Take 30-60 of largest larvae • Vials labeled inside and out using pencil • a) case # • b) collection time • c) date • d) geographic location • e) location of insects on victim • f) initials of investigator