Chapter 12 Forensic Entomology. Case study – Bugs Don’t Lie 1. When did the children go missing? 2. When were the bodies found? 3. List 5 reasons for.

Chapter 12Forensic

Entomology

Case study – Bugs Don’t Lie

1. When did the children go missing?2. When were the bodies found?3. List 5 reasons for suspecting the stepfather.4. Summarize the entomological evidence and

explain how this lead to estimating the time of death.

IntroductionO Forensic entomology – use of insects

in legal investigationsO Phylum Arthropoda – insects,

spiders, scorpions, crayfish, and millipedes

- invertebrates - externally segmented bodies - exoskeleton made of chitin

Historical DevelopmentO Fig. 12-3 p. 344O 1st documented use of insect

evidence to solve crime China in 1235

Insects and ForensicsO Head – brain, antennae, eyes, and

mouthpartsO Thorax – 3 prs. of legs and possibly 2

prs of wingsO Abdomen – reproductive and

digestive organsO 29 orders of insects – flies and

beetles most important to forensics

Insect OrdersO Flies – DipteraO - found in almost every

environmentO ex) blowflies – found at 1st stages

of decompositionO 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

Insect OrdersO Beetles – ColeopteraO - most prominent in later

stages of decompositionO Final stage = skeletal – beetles are

joined by other soil-dwelling insects O See Fig. 12-5 p. 346

Insects at WorkO Life cycle – egg larva(feeding

stage) pupa(relatively inactive, nonfeeding stage)

O Abiotic and biotic factors interact to maintain balance in an ecosystem

O AF = sun, atmosphere, weatherO BF = organisms or remains of

organisms

There is strength in numbers

O 1 million species of insectsO Short lifespan but produce large

numbers of eggsO Contribution to ecosystem =

loosening of soil, pollination, consuming plant pests

O Incomplete metamorphosis – nymph(wingless) molts several times adult

O Meteorology vs climatology

Postmortem Interval(PMI)

O Need to establish timeline of eventsO PMI is an important element of that

timelineO http://www.pbs.org/wnet/nature/

episodes/crime-scene-creatures/interactive-determine-the-time-of-death/4390/

Collecting and Preserving Entomological EvidenceO Include info about rainfall and temperatureO Investigation team collects evidence and

sends it to the forensic entomologist at the lab

O 1. Start collection several feet away from the body

O 2. measure distance between insect evidence and body

O 3. collect samples at all stages on, near, or under body

O 4. at lab – raise samples at same conditions as crime scene

What to recordO 1. temperatureO 2. type and amount of precipitationO 3. type and amount of lightO 4. humidityO 5. amount and direction of wind

TemperatureO An increase in temperature = an

increase in insect developmentO A)ambient - 1 and 4 feet above the

bodyO B) soil – surface, 10 cm. below

surface, and 20 cm below surface

More on collecting and preserving evidence

O Nets for flying stageO Pinned or transferred to vial in

80%alcoholO Take 30-60 of largest larvaeO Vials labeled inside and out using pencilO a) case #O b) collection timeO c) dateO d) geographic locationO e) location of insects on victimO f) initials of investigator