Forensic Entomology

Forensic entomology

“any aspect of the study of arthropod counterparts that interact with legal matters” (Hall, 1990)

What is the main type of estimate that forensic entomology can provide?

Post Mortem Interval (PMI)

Other than PMI, entomology can provide evidence about what?

• peri-mortem trauma

• child and elderly abuse

• movement of body (indoors vs. outdoors)

• extraneous drugs and toxins

• insect and victim DNA

Two key tasks at the scene regarding temperature and PMI estimation

1.) comprehensively recording scene temperature regimes

2.) comprehensively document other contextual and environmental factors that could affect insect development

Insects are exothermic (poikilotherms), which means what?

• cannot control temperature internally

• metabolic rates determined by ambient temperature

• rate of development will depend on temperature regime

• specific insect ecology and physiology

What entomology clues can be used to make a child and elderly abuse case?

• maggots/eggs in diapers and clothing indicating neglect

• time span without a diaper/clothing change can be estimated in the same manner as PMI

What entomological evidence can be used to support peri-mortem trauma?

Flies colonize exposed mucosa post-mortem (natural orifices), but the presence of maggot masses in other areas signal broken skin (i.e., trauma)

What is an example of how entomological evidence can be used to support the movement of a body after death?

Ex. body buried at an outdoor scene, but only colonized by indoor fly species (Musca domestica)

• indoors vs outdoor species

• rural vs urban species

• habitat distribution

Entomology and extraneous drugs and toxins?

• drugs detectable in maggots and cuticle of puparia even after millennia

• also detectable in development pattern of larvae

DNA of insect and victim?

• larval DNA matching population of specific location

• victim DNA identified from puparia

Subphylum: Chelicerata (MAP)

• Class Merostomata (horseshoe crabs, eurypterids)

• Class Arachnida (spiders, ticks, mites, scorpions)

• Class Pycnogonida (sea spiders)

Subphylum: Crustacea (5)

• Class Remipedia

• Class Cephalocarida

• Class Branchiopoda (fairy shrimp, water fleas, etc.)

• Class Maxillopoda (ostracods, copepods, barnacles)

• Class Malacostraca (isopods, amphipods, krill, crabs, shrimp, etc.)

Subphylum: Uniramia (ICD)

• Class Insecta (head+thorax+abdomen)

• Class Chilopoda (centipedes) (head+trunk)

• Class Diplopoda (millipedes) (head+trunk)

In Forensic Anth, our goal is not identifying insects, but to ______ insects

collect (using the outdoor scene data collection form, which has a section on entomological data)

Phylum Arthropoda

crustaceans, insects, spiders, and relatives

PMI Estimation: Main method based on physiological temperature

Combination of temperature data and insect physiology and development

T/F All insects/arthropods are equally useful for physiological temperature PMI

False; it depends on the reproductive/life cycle of the insect

What are the three types of insect life cycles?

1.) Ametabolous

2.) Hemimetabolous

3.) Holometabolous

Ametabolous

undifferentiated nymph, no maggot

Hemimetabolous

differentiated nymph, but no maggot

Holometabolous

maggots and puparia

Which insect life cycle is best for PMI estimation?

Holometabolous

Class Insecta: Subclass Apterygota examples

bristletails, snowflies, springtails, diplura, and anoplura: wingless insects!

(Insecta) Ametabolous development

little or no metamorphosis; the nymphs are small versions of the adults

→ Age estimates must be based on size: more variability and less precise