msc presentation on Forrensic entomology

3. FORENSIC ENTOMOLoGY
• Forensic entomology is the application and
study of insects and other arthropods biology
to legal issues, especially in a court of law.
• Flies and beetles follow a life cycle that allow
scientists to estimate how long a body has
been deceased.

4. History of Forensic Entomology
• Sung Tz'u (1235 AD) – Chinese “death investigator” wrote
“The Washing Away of Wrongs”.
• First forensic entomology case recorded -
A murder by slashing occurred in a village, and the local
death investigator was ordered to solve the crime. The
investigator had all villagers bring their sickles to one spot
and lay them out before the crowd. Flies were attracted to
one of the sickles, probably because of invisible remnants of
tissue still remaining on it, and the owner subsequently
broke down and confessed to the crime.

5. What do Forensic
Entomologists Do?
• Forensic Entomologists apply their knowledge of entomology to
provide information for criminal investigations.
• A forensic entomologist’s job may include:
– Identification of insects at various stages of their life cycle,
such as eggs, larva, and adults.
– Collection and preservation of insects as evidence.
– Determining an estimate for the postmortem interval or PMI
(the time between death and the discovery of the body) using
factors such as insect evidence, weather conditions, location
and condition of the body, etc.
– Testifying in court to explain insect-related evidence found at a
crime scene.

6. Insects as Evidence
• Most insects used in investigations are in two
major orders:
1 – Flies (Diptera) and
2 – Beetles (Coleoptera)
• Species succession may also provide clues for
investigators. Some species may to feed on a
fresh corpse, while another species may prefer
to feed on one that has been dead for two
weeks. Investigators will also find other insect
species that prey on the insects feeding on the
corpse.

7. Determination of pmi -
• PMI means Postmortem Interval (the time
between death and the discovery of the body)
• Determination of PMI is based on two major
principles:
1. SUCCESSION
2. LIFE CYCLE OF FLY

8. Five Stages of Decomposition Fueled by Insect Activity.
• Fresh
• Bloat
• Decay
• Post-decay
• Dry (skeletal)

9. 1.Fresh Stage
• Begins at death.
• Flesh flies, blow flies, ants eating fly eggs and
predatory wasps.
• First sign of bloating due to putrefaction by
anaerobic bacteria.
• Autolysis, the degradation of complex protein
and carbohydrate molecules, occurs.

10. Pig carcass in the fresh stage of decomposition

11. 2.Bloat
• Swells due to gases
produced by bacteria
• Temperature rise of the
corpse
• Flies still present adult
and larval blowflies
attracted in large
numbers to seepage &
soil fauna moves away
due to wetness of earth;
ants and other species of
flies prey on maggots.Pig carcass in the bloat stage of
decomposition

12. 3.Decay
• Gases subside,
decomposition fluids
seep from body.
• Bacteria and maggots
break through the skin.
• Predatory beetles such as
rove and hister beetles are
attracted
• Unpleasant odor
• Larvae beginning to
pupate.
• Corpse reduced to about
20% of it’s original mass.
Pig carcass in the decay stage of
decomposition

13. 4.Post-Decay
• Carcass reduced to hair, skin, and
bones.
– in dry habitats - remains
consist of dry skin, cartilage
and bones; site for dermestid
beetles, histerids, fly pupae,
immature and adult rove
beetles
– in wet habitats – large
quantities of wet, viscous
material (byproducts of
decomposition) found in soil
under the remains; site for
adult and immature moth flies,
rove beetlesPig carcass in the post-decay stage of
decomposition

14. 5.Dry (Skeletal)
• Does not always occur especially if corpse
is in a wet region. Maggots will stay
longer and hide beetles will not appear.
• The corpse is reduced to at least ten
percent of the original mass.
• In the last stage (Skeletal Stage), only
bone and hair remain.
• some dermestids, fly pupae, immature
and adult rove beetles, normal soil fauna
consisting of mites, etc. start to return;
this stage could last for several months to
years.

15. Pig carcassinthe dry/remainsstageof decomposition

16. life cycle of blow fly-

17. Collection of entomological evidence -
• Camera & video, to fix the evidence site.
• Net to catch fly, etc. Sticky traps are also used instead.
• Collection of paraphernalia: Live specimen containers, killed
creatures container jar, forceps, spoon , small paint-brushes.
• Preservation usually 98% alcohol (ethanol) is used.
• Recording materials like labels, pencil, ruler, crime scene from , if
any, prescribed by authorities.
• Gloves and hand towels are usually taken along to maintain
hygiene.

19. FACTOR AFFECTING PMI-
• Night Time & cold temperature.
• Rain.
• Physical prevent insect from reaching a
corpse can delay as- Storage in sealed
container or wrapping, submergence of
water etc.

20. refrences-
• Journal of forensic dental science
• B. r. sharma, Forensic science in criminal investigation & Trials
• https://en.wikipedia.org/wiki
• encyclopedia of forensic sciences three-volume set 1-3