Entomology

Introductiono Entomology is the study of

insectso Forensic entomology is the

study of the insects associated with a dead bodyo Also known as medicolegalo 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 o Insects begin colonizing at

a dead body immediately after deatho Dependent on season and

environment

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

year

Introduction o Entomological evidence is

the most accurate and frequently the only method available to determine the elapsed time since deatho Due to rigor, algor, and livor

mortis being useless after 72 hours

Introduction o Insects are also used to

o Determine whether the body has been moved after death

o Determine whether it has been disturbed

o Determine the presence or position of wound sites

o Determine whether the victim used drugs or was poisoned

o Determine the length of time of neglect or abuse in living victims

Importance of Determining Time Since Death

o Important for the family of the deceasedo 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

o Timing of death may also have legal implicationso Insurance policies

oWhether death occurred before or after insurance coverage began

o Important for families when money is involved

Importance of Determining Time Since Death

o May indicate the length of time that a fraud has occurredo Receiving monies for family

members while family members are deceased

History of Entomologyo Is one of the oldest forensic

sciences used in death investigations

o First recorded use was in 13th century China

o Modern use of entomology in criminal investigations began in France in the mid 1800s

o First reported use of forensic entomology in North America was in Quebec in 1897o Did not become common until 1970s

History of Entomologyo American Board of

Entomology was established in 1996 by Dr. Paul Catts and Dr. Lee Goff

o European Association of Forensic Entomology was established in 2001

Trainingo Must have extensive training in

entomologyo Bachelors degree in biology,

zoology, or entomologyo Masters in entomologyo PhD in forensic entomology, insect

ecology, and taxonomyo Board certification requires 5 years

of experience after PhD

o Most forensic entomologists are university professors

Employmento Forensic entomologists do

not work full time for crime labso Primary employment is in

research and teachingo Therefore, most have little or

NO experience with crime scenes, legal report writings, or court testimonies

Decompositiono Begins at the moment of

death, caused by two factorso Autolysis

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

o PutrefactionoThe breakdown of tissues by

bacteria oThese processes release gases

that are the chief source of the characteristic odor of dead bodies

o These gases swell the body

Decompositiono Scavengers play an important role in

decompositiono Insects and other animals are typically

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

o The most important insects that are typically involved in the process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae)o The green-bottle fly seen in the summer is a

blowfly

o Larger scavengers, including coyotes, dogs, wolves, foxes, rats, and mice may eat a body if it is accessible to themo Some of these animals also remove and

scatter bones.

Factors Involved in Decompositiono In a roughly descending degree of

importance, those factors include:o Temperature o The availability of oxygen o Prior embalming o Cause of death o Access by insects o Burial, and depth of burial o Access by scavengers o Trauma, including wounds and crushing

blows o Humidity, or dryness o Rainfall o Body size and weight o Clothing o The surface on which the body rests

Determination of Elapsed Time Since Death

o First method based on the predictable development of larval Diptera, known as the blow flyo Used from the first time the

first egg is laid on the remains until the first adult flies emerge from the pupal cases and leave the bodyoEvidence valuable from a few

hours to several weeks after death

Determination of Elapsed Time Since Death

o Second method is based on the predictable, successional colonization of the body by a sequence of carrion insectso Can be used from a few weeks

after death until nothing but dry bones remain

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Blow Flieso Blow flies are the first flies

to be attracted to a bodyo They are large, metallic flies

seen near food or garbage cans in summer

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

Blow Flieso Male and female blow flies

require a protein meal before the ovaries and testes develop and oogenesis and spermatogenesis can occuro Adult feeding may occur at

the dead bodyo Majority of the flies attracted

to remains are females searching for egg laying sites

Blow Flieso Blow flies develop from

eggs through the first, second, and third instar stages, and then the pupal stage before becoming adults

o Stages influenced by species of blow flies and temperature of surroundings

Blow Flieso Insects are cold-blooded so

their development is temperature dependento As temperature increases,

they develop more rapidlyo As temperature decreases,

they develop more slowly

Blow Flieso Analysis of the oldest insect

stage on they body, together with knowledge of the meteorological conditions at the scene, can be used to determine how long insects have been feeding on the body, and hence, how long the victim has been dead

First Instar Stageo Once blow fly eggs have been laid,

they will hatch into first instar larvae

o Larvae rely on protein for their mealso Females lay eggs on open wounds of

dead individuals or around orifices of a living individual

o Face is colonized before other areas because the skin is easier to penetrateoExcept in the case of rape cases, flies

attracted to genetalia

Second Instar Stageo First instar larvae shed

larval cuticle and mouthparts when entering second instar stageo Is more capable of

penetrating the skin than the first instar larvaeoDoes so with proteolytic

enzymes

Third Instar Stageo Third instar stage begins with

second instar larvae shedding its cuticle

o Are called maggotso Maggots aggregate together in

large masseso Can remove a large amount of

tissue in a very short amount of time

o After feeding, the maggots move on to a site where they can pupateo Remove outer cuticle so they can

emerge as a fly

Time Spano Female lays 2,000 eggs in

her lifetimeo Once eggs are laid, they

hatch between 12 and 48 hours

o It takes 14 days for the fly to emerge from the pupal case

Factors Used to Determine Time Since Death

o 4 factors must be taken into account o Oldest stage of blow fly associated

with the bodyo Look at old pupal cases

o Species of insectso Each species develop at different rates

so each species of insects at the scene need to be collected

o Temperature datao Must be able to determine temperature

of crime scene for a period of time

o Developmental datao Must know how fast or how slow the

specific species develop

Determining Whether the Body has been Moved

o Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location

Presence and Position of Wounds

o Insects are attracted first and foremost to wounds so the first instar larvae will have access to liquid protein for nutrition

o Wound sites in individuals that have completely decomposed are shown by irregular or atypical insect colonization

Linking Suspect to Sceneo Sometimes, criminals carry

entomological evidence on them unknowingly

o This evidence can place them at the crime scene by examining the life cycles of the insects

Drugso Insects that feed on the body

of individuals that have been poisoned can be examined to determine what type of drug or toxin the person was poisoned witho It is important to note that

specific drugs either speed up or slow down larval developmentoCan influence entomologist’s final

report

Collection of Entomological Evidence

o Evidence should be collected by an entomologist o If not available, a police death

investigator should collect the evidence

o Different stages of larval growth should be collected and bagged separately

o Sample of soil should also be collected from just outside the area marked by body fluids

Challenges to Forensic Entomology

o 3 challenges existo Temperature

oTemperature of crime scene and the temperature that the insects have been exposed to us unknown

o SeasonoEntomology is valuable only in

spring, summer, and fall

o Exclusion of insectso Insects are excluded based on

condition of body