Forensic Entomology

David Shetlar(the BugDoc)

Urban Landscape EntomologistThe Ohio State University

shetlar.1@osu.edu

What is Forensic Entomology?

The study and use of arthropods (including insects) as evidence in criminal or other legal investigations.

Forensic Entomology is commonly divided into three fields:

1. Medico-Legal

2. Urban

3. Stored Products - Foods

Forensics Entomology

Medico-Legal Cases

Necrophagous arthropods – those that find and feed on decaying animal flesh. Arthropods are often used to estimate the Post Mortem Interval (PMI).

Taphonomy – study of a decaying organism over time (originally used by paleontologists and archaeologists).

Insect Growth & Developmentand Species Succession

in Estimating PMI• Arthropods are poikilothermic (metabolic

rate largely determined by temperature).

• We have established development models (temperature dependent) for insect species and their stages.

• Different insect species and groups colonize dead and decaying animals in a predictable order.

Characteristics of the PhylumArthropoda

• The segmented bodies are arranged into regions, called tagmata (e.g., head, thorax, abdomen).

• The paired appendages (e.g., legs, antennae) are jointed.

• They posses a chitinous exoskeletion that must be shed during growth.

• They have bilateral symmetry.

• The nervous system is ventral (belly) and the circulatory system is open and dorsal (back).

Class Hexapoda(the insects)

• Three tagmata – head, thorax, abdomen

• Thorax with three pairs of legs; normally two pairs of wings in adult stage

• Head with one pair of antennae

• Respiration by trachea

• Terrestrial & fresh water inhabitants

Class Hexapoda(all have one pair of antennae, a head, thorax &

abdominal regions, three pair of legs, adults usually have wings, use trachea)

Life Cycle Groups

• Simple Metamorphosis (=incomplete) - egg, nymph, adult stages

• Complete Metamorphosis - egg, larva, pupa, adult stages

Incomplete Metamorphosis Example(hairy chinch bug)

egg 1st 2nd 3rd 4th 5th adult instar instar instar instar instar

Egg Nymphal AdultStage Stage Stage

Incomplete Metamorphosis Example(hairy chinch bug)

egg 1st 2nd 3rd 4th 5th normal wing short wing instar instar instar instar instar adult adult

Egg Nymphal AdultStage Stage Stage

Complete Metamorphosis Example(May/June beetle)

egg 1st 2nd 3rd pupa adult instar instar instar

Egg Larval Pupal AdultStage Stage Stage Stage

Complete Metamorphosis Example(northern masked chafer)

egg 1st 2nd 3rd pupa adult instar instar instar

Egg Larval Pupal AdultStage Stage Stage Stage

Hexapod OrdersEntognathous Hexapods –

Order Protura

Order Collembola

Order Diplura

Ectognathous apterygote Hexapods –

Order Microcoryphia

Order Thysanura

Pterygote Hexapods –

(simple metamorphosis)

Order Ephemeroptera

Order Odonata

Order Orthoptera

Order Phasmatodea

Order Dermaptera

Order Plecoptera

Order Isoptera

(simple metamorphosis cont’d)

Order Mantodea

Order Blattodea

Order Hemiptera

Order Thysanoptera

Order Psocoptera

Order Phthiraptera

(complete metamorphosis)

Order Coleoptera

Order Neuroptera

Order Hymenoptera

Order Trichoptera

Order Lepidoptera

Order Siphonaptera

Order Diptera

Common Insect SuccessionOn a Carcass

• Calliphorid (blow) flies (within hours)

• Muscid (house) flies (within hours or days, depending on wounds)

• Piophilid (cheese skippers) (upon putrification)

• Staphylinid, hister, silphid beetles (not normally used, often maggot predators)

• Dermestids (feed on hide and hair)

Calliphoridae (blow flies)

Cynomya cadaerina, blue blow fly

Lucilia (Phaenicia) sericata,

green blow fly

House fly, Musca domestica

Piophila casei (a cheese skipper)

Staphylinidae (above) & Histeridae (right) are common predators of

maggots and other insects

Silphid beetles are often called carrion beetles and some are called burring beetles because they bury small dead animals to rear their young!

Necrophila americana

Thanatophilus lapponicus

Dermestidae (skin, hide, larder beetles)

Crime Scene Protocols

• Close coordination with other crime scene investigators (avoid contamination, allow other investigators to collect primary evidence, follow legal protocols).

• Collection of insects in and on carcass.

• Collection of insects in soil or area under and around carcass.

• Collection of insects flying or resting in area.

• Document, document, document! – chain of evidence, etc.

Collecting Entomological EvidenceAt Crime Scene

• Visual observations and notes of scene.

• Climatological data (current conditions).

• Collection of specimens in and around body.

• Post-body removal (sub-soil temps, leave data logger, collection of additional specimens).

Crime Scene ObservationsAnd Notes

• Written notes with general map of scene.

• Photographic evidence showing scale.

• Estimation of types of insects and locations on and off the body.

• Document conditions that may modify how insects find the body or develop.

Climatological Data (Current)At Crime Scene

• Ambient air temperature

• Ambient humidity

• Ground surface temperature

• Body surface temperatures

• Below-body temperatures

• Maggot mass temperatures

Collecting Specimens InAnd Around Body

• Sweep net – capturing insects flying or resting around the scene (up to 20 feet).

• Hand capture (forceps and spoons) of surface insects (eggs, maggots, beetles, etc). AVOID DAMAGING OTHER EVIDENCE!

• After body removal, dig in soil or other underlying substrate (larvae and pupae).

• Save live and preserved specimens

• Document, document, document!

Insect Handling & Preservation

• LABEL ALL SPECIMENS ON SITE! (soft graphite pencil or alcohol proof ink pen).

• Flying insects (stun or kill in ethyl acetate killing jar) – preserve in 70%+ ethanol (allows DNA sampling).

• Maggots – keep some alive for rearing; rest, heat “blanch” in hot water, then in ethanol.

• Pupae – rear and preserve in ethanol.

• Beetle adults and larvae – preserve in ethanol.

Bunny Forensics! (three baby rabbits found freshly killed on 20 April; one was placed on sand in open container, one was placed on fine soil in open container, and one was placed on bare soil; all covered by ½-inch mesh wire frame; maggots collected on 2 May) ABOVE: maggots from sand.

Cephalopharyngeal skeleton of first maggot.

Posterior spiracle of first maggot.

Cephalopharyngeal skeleton (and anterior spiracle) first maggot(cleared in KOH & placed in Hoyer’s media on slide)

Posterior spiracle of first maggot(cleared in KOH & placed in Hoyer’s media on slide)

Lucilia (Phaenicia) sericata, common green blow fly

(green bottle fly)

Bunny Forensics: maggots from rabbit on fine soil. When placed in container, one of the maggots was observed to JUMP!

Second maggot cephalopharyngeal skeleton & posterior

spiracle

Piophila casei – a cheese skipper

CALCULATING A PMI• Main reason

for studying presence and life stages of insects on a corpse is to establish the time since death

From: Greenberg, B. 1991. Flies as forensic indicators. J. Med. Entomol. 28(5): 565-577

CALCULATING A PMI

– Computer simulation programs are often used in estimating PMI

Case Study“Maggot Boy”

Plaintiffs: early teens boy and parent

Defendants: fast food restaurant local owner & corporate

Alleged:Picked up son from school (Monday)Stopped by restaurant on way homePurchased three hamburgers (one eaten on way home)Son began to eat second hamburger (about 5pm)Daughter screamed that his mouth was full of maggots! Hamburger was infested when purchased

Evidence: submitted three maggots in 70% EtOH

Case Study“Maggot Boy” (cont’d)

Evidence Analysis:Maggot 1 = 7.28mmMaggot 2 = 7.28mmMaggot 3 = 6.11mm (slightly curved & distorted)

Maggots subjected to KOH clearing and microscopic examination found cephalopharyngeal skeleton consistent with third instar Phaenicia sericata

Located NOAA weather for five days prior to claimed maggot discovery and recorded hourly temperatures.

Case Study“Maggot Boy” (cont’d)

Development Back Tracking:Maggot size suggests about 72 hour old if developing at 21 C (~1512 degree-hours)

Back Calculating from claimed discovery time, eggs would have been laid between 15:00 and 19:00 on the previous Friday!

Report Submitted to Defendant’s Lawyer who forwarded to Plaintiffs’ Lawyer.

Case Study“Maggot Boy” (cont’d)The Rest of the Story!

Parent’s partner has fight after reading report and pair breaks up!

Calls Defendant’s Lawyer and states that hamburgers were purchased on FRIDAY on way home, not Monday.

Son left out hamburger all weekend and decided to eat it after getting home from school on Monday!

Case Dropped!

Case Study“Snakes, Rats & Maggots!”

Plaintiffs: new home owners, couple in their late 20s.

Defendants: previous owners, couple in their mid-20s.

Alleged:House severely infested with adult flies (like Amityville

Horror!)Previous owner didn’t disclose that he raised snakes in

basement!Rats (for food) must have gotten loose and died, thereby

producing the flies!

Evidence: submitted three pictures of dead flies on basement floor and hallway stairs. Eventually a half dozen dead adult flies submitted.

OTHER FORENSIC USES FOR INSECTS

• Ingestion of drugs, toxins, or other substances from body

• DNA may be obtained from guts of insects

• May give information about the location, travel, or geography associated with items

SOME FINAL COMMENTS! • Only about 70 certified forensic entomologists in

the United States!• Over half are associated with universities, the

rest are private consultants and a very few are associated with law enforcement agencies.

• Genetic fingerprinting has made maggot identification easier, but this is still very expensive and few labs can do the work so most do identifications the old fashion way!

• Most forensic entomologists get specimens from other agencies for identification and analysis.

• You must be a detail and protocol person!

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