Forensic Entomology David Shetlar (the BugDoc) Urban Landscape Entomologist The Ohio State University [email protected]
Jan 20, 2016
Forensic Entomology
David Shetlar(the BugDoc)
Urban Landscape EntomologistThe Ohio State University
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!
Come visit the BugDoc at:Come visit the BugDoc at:http://bugs.osu.eduhttp://bugs.osu.edu