Forensic Entomology

Dead men do tell tales……

2 Forensic Science II: Forensic Entomology,

Chapter 12

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Introduction—Vocabulary

Arthropod—a phylum of animals with jointed appendages and an exoskeleton (from the Greek arthros–jointed; podes–feet)

chitin—a tough polysaccharide; the major component of an arthropod’s exoskeleton

exoskeleton—a rigid external structure made of chitin and protein (protects, provides a point of attachment for muscles; prevents water loss)

forensic entomology—the study of insects in legal situations

3 Forensic Science II: Forensic Entomology,

Chapter 12

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Introduction—Vocabulary

invertebrate - organism lacking a backbone

larva (larvae, pl) - immature, feeding stage of insects that undergo complete metamorphosis; the stage between the egg and pupa

maggot - legless larva

metamorphosis - the changes an organism undergoes as it develops into an adult

pupa (pupae, pl) - nonfeeding and relatively inactive developmental stage of some insects

4 Forensic Science II: Forensic Entomology,

Chapter 12

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Introduction (Obj 12.1, 12.2)

Arthropod—an invertebrate

Introduction

Entomology is the study of insects Forensic entomology is the study of

the insects associated with a dead body Also known as medicolegal Forensic entomologists are called into

homicide investigations when time of death is unknown and their evidence is usually presented in court as expert testimony

Introduction

Insects begin colonizing at a dead body immediately after death Dependent on season and environment

Rate of development of the species can be used to estimate time since death Can give an estimate up to a year

Introduction

Entomological evidence is the most accurate and frequently the only method available to determine the elapsed time since death Due to rigor, algor, and livor mortis being

useless after 72 hours

Introduction

Insects are also used to Determine whether the body has been

moved after death Determine whether it has been disturbed Determine the presence or position of

wound sites Determine whether the victim used drugs

or was poisoned Determine the length of time of neglect

or abuse in living victims

Importance of Determining Time Since Death

Important for the family of the deceased Understanding how, when, and why a

person has died can help to give closure to family and friends and allow them to move on with their lives

Importance of Determining Time Since Death (Legal)

Timing of death may also have legal implications Insurance policies

Whether death occurred before or after insurance coverage began

Important for families when money is involved

May indicate the length of time that a fraud has occurred Receiving monies for family members while

family members are deceased

11 Forensic Science II: Forensic Entomology,

Chapter 12

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History

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 (Egg to larva to pupa to insect)

Larvasoft tubular body and look like worms. Fly species larvae are “maggots”

Image: http://www.nlm.nih.gov/visibleproofs

Decomposition

Begins at the moment of death, caused by two factors Autolysis

The breaking down of tissues by the body's own internal chemicals and enzymes

Putrefaction The breakdown of tissues by bacteria These processes release gases that are the

chief source of the characteristic odor of dead bodies These gases swell the body

Decomposition

Scavengers play an important role in decomposition Insects and other animals (scavengers) are

typically the next agent of decomposition, if the body is accessible to them

The most important insectsfleshflies (Sarcophagidae) and blowflies (Calliphoridae) The green-bottle fly seen in the summer is a

blowfly Larger scavengers, including coyotes, dogs,

wolves, foxes, rats, and mice may eat a body if it is accessible to them Some of these animals also remove and scatter bones.

Factors Involved in Decomposition

In a roughly descending degree of importance, those factors include: Temperature The availability of oxygen Prior embalming Cause of death Access by insects Burial, and depth of burial Access by scavengers Trauma, including wounds and crushing blows Humidity, or dryness Rainfall Body size and weight Clothing The surface on which the body rests

Post-Mortem Interval (PMI)

Time between death and the discovery of the body.

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. Closed windows Body in box or bag Cold temperatures Deeper burial

Major Groups of Insects Associated with Cadavers

Flies Blowflies Flesh Flies House Flies Cheese Skippers

Beetles Carrion Beetles Dermestids Scarab Beetles

Blow Flies

Blow flies are the first flies to be attracted to a body

They are large, metallic flies seen near food or garbage cans in summer

Blow flies belong to the family Calliphoridae, in the order Diptera or “true flies”