AL-NEELAIN UNIVERSITYFACULTY Of Medical Laboratory Sciences

PARASITOLOGY AND MEDICAL ENTOMOLOGY

FORENSIC ENTOMOLOGY

PRESENTED BY`

MUSA. A. ALI. A. GINDEEL. (BSC.MSC STUDENT)

Symposium on: Advances in Parasitology “Education and Research in Parasitology in the service of Mankind “ 28 MARCH 2015

Maggots and Time of Death Estimation

FORENSIC ENTOMOLOGY

Entomology is the Study of Insects

What is Forensic Entomology?

• Forensic Entomology is the use of the insects and other arthropods that feed on decaying remains to aid legal investigations. (Medicolegal criminal)

History of Forensic Entomology

• Is one of the oldest forensic sciences used in death investigation

• First recorded use was in 13th century in China• First report in North America was in Quebec in

1897• American Board was established in 1966• European Association was established in 2001

Medicolegal Forensic Entomology

• Use to ;– Determination of the time (postmortem interval

or PMI) or site of human death based on identification of arthropods collected from or near corpses.

– Traffic accidents with no immediately obvious cause

– Possible criminal misuse of insects

Insects as EvidenceForensic entomologists use their knowledge of insects and their life cycles and behaviors to give them clues about a crime.

Most insects used in investigations are in two major orders:1 – Flies (Diptera).2 – Beetles (Coleoptera)

Blow Fly

Carrion Beetle

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 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.

What do they do?

Insect Biology

• Insects are the most diverse and abundant forms of life on earth.

• There are over a million described species- more than 2/3 of all known organisms

• There is more total biomass of insects than of humans.

• Insects undergo either incomplete or complete metamorphosis.

• Larva have a soft tubular body and look like worms. Fly species larvae are “maggots”

Postmortem interval (PMI)

• Forensic Entomology is used to determine time since death (the time between death and corpse discovery)

• This is called postmortem interval or PMI).• Other uses include

• movement of the corpse• manner and cause of death• association of suspects with the death scene• detection of toxins, drugs, or even the DNA of the

victim through analysis of insect larvae.

factors that might affect their PMI estimates:

• Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs (body in box or bag)

•Were other insect species present that may have affected the development of the collected species

•Were there drugs or other poisons in or on the body that might have affected the larvae’s development

• Deeper burial

Differentiate between PMI and Time of Death

• These may not always equate. • Post mortem interval is restricted to the time

that the corpse or body has been exposed to an environment which would allow insect activity to begin.

Succession of Insects on the Corpse

• Ecological succession occurs as an unexploited habitat (like a corpse) is invaded by a series of different organisms.

• The first invasion is by insect species which will alter the habitat in some form by their activities. These changes make the habitat attractive to a second wave of organisms which, in turn, alter the habitat for use by yet another organisms.

Examples of Diptera (Flies)

Flesh Fly(Sarcophagidae)

Striped thorax

Blow & Greenbottle Flies

(Calliphoridae)Metallic thorax and abdomen

House Fly(Muscidae)

Cheese Skipper (Piophilidae)

Early Stage Decomposition

Late Stage Decomposition

Life Cycle of a Calliphoridae Fly

Blow Fly Metamorphosis

1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc.

2nd – Eggs hatch into larva (maggots) in 12-24 hours.

3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages. 1st Instar - 5 mm long after 1.8 days 2nd Instar - 10 mm long after 2.5 days 3rd Instar – 14-16 mm long after 4-5 days

4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil.

5th – Adult flies emerge from pupa cases after 6-8 days.

Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages.

It takes approximately 14-16 days from egg to adult depending on the

temperatures and humidity levels at the location of the body.

Adult

EggsPupa

3rd Instar Larva

2nd Instar Larva

1st Instar Larva

Examples of Coleoptera (Beetles)

Carrion Beetles (Silphidae)Adults & larvae feed on fly larvae

Early to Late Stage Decomposition

Late Stage Decomposition

Rove Beetles (Staphylinidae)

Predator of fly eggs

Early Stage Decomposition

Hide Beetles (Scarabidae)

Usually the last to arrive

Clown Beetles (Histeridae)

Predator of fly eggs

Ham & Checkered Beetles (Cleridae)

Predator of flies & beetles; also feed on dead tissue Skin Beetles (Dermestidae)

Feed on dried skin & tissues

Forensic Entomology is Applied Biology

• If it weren’t for decomposition of all living things, our world would fill up with dead bodies.

Did you know…The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate.

Ecology of Decomposition

• Necrophages - the first species feeding on corpse tissue. Includes true flies (Diptera) and beetles (Coleoptera).

• Omnivores - species such as ants, wasps, and some beetles that feed on both the corpse and associated maggots. Large populations of ominvores may slow the rate of corpse’s decomposition by reducing populations of necrophagous species.

• Incidentals – pill bugs, spiders, mites, centipedes that use the corpse as an extension of their normal habitat

Decay Rates Are Variable

• Most important environment factors in corpse decay: • Temperature• Access by insects• Depth of burial

• Other Factors• Chemical-- embalming agent, insecticides, lime,

etc.• Animals disrupting the corpse

Five Stages of Decomposition Fueled by Insect Activity.

• Fresh• Bloat• Decay• Post-decay• Dry (skeletal)

Fresh• Begins at death• Flies begin to arrive• Temperature falls to that

of the ambient temperature.

• Autolysis, the degradation of complex protein and carbohydrate molecules, occurs.

Bloat

• Swells due to gases produced by bacteria

• Temperature rise of the corpse

• Flies still present

Decay• Gases subside,

decomposition fluids seep from body.

• Bacteria and maggots break through the skin.

• Large maggot masses and extreme amounts of fluid.

• Unpleasant odor• Larvae beginning to

pupate.• Corpse reduced to about

20% of it’s original mass.

Post-Decay• Carcass reduced to

hair, skin, and bones.• Fly population

reduced and replaced by other arthropods.

• Hide beetles are dominant in dry environments.

• Mite and predatory beetle populations increase.

Dry (Skeletal)• Does not always occur especially if corpse is in

a wet region. Maggots will stay longer and hide beetles will not appear.

• In wet environments the hide beetles are replaced with other insects.

• In the last stage (Skeletal Stage), only bone and hair remain.

Two Different Maggot Generations

• These are distinguishable by the length and obvious size difference.

Challenge to Forensic Entomology

Temperature of crime scene and temperature that the insect have been exposed to us unknown

Exclusion of insects by; -animal -first attendance to crime scene -refrigerate the corpse before collection the

sample

Thank You