Forensic Entomology

The Study of the Insects The Study of the Insects Associated with a Dead BodyAssociated with a Dead Body……

Why Are Insects Used in Forensic Why Are Insects Used in Forensic Science?Science?

• In most seasons and environments, In most seasons and environments, insects colonize a dead body almost insects colonize a dead body almost immediately after deathimmediately after death

• Their rate of development and species Their rate of development and species dynamics over time can be used to dynamics over time can be used to accurately determine time since death.accurately determine time since death.

• After 72 hours, entomological evidence After 72 hours, entomological evidence is the most accurate method to is the most accurate method to determine the elapsed time since death.determine the elapsed time since death.

The History of Forensic Entomology

• 11stst recorded use: 13 recorded use: 13thth century China century China

• Became quite commonly used in Europe Became quite commonly used in Europe throughout the 20throughout the 20thth century century

• Popularity increased in North America in Popularity increased in North America in the 1970’sthe 1970’s

• Today: used quite extensively and Today: used quite extensively and commonly in homicide investigations.commonly in homicide investigations.

What Can Insects Tell you?What Can Insects Tell you?

• Post mortem intervalPost mortem interval

• Whether the body was moved after deathWhether the body was moved after death

• Whether the body was disturbed Whether the body was disturbed

• Presence and position of wound sitesPresence and position of wound sites

• If the victim used drugs or was poisonedIf the victim used drugs or was poisoned

• Length of time of abuse or neglect in living Length of time of abuse or neglect in living victimsvictims

Determination of Elapsed Time Determination of Elapsed Time Since DeathSince Death

Two Methods:Two Methods:• Method #1: BlowfliesMethod #1: Blowflies are attracted to a are attracted to a

body immediately following deathbody immediately following death– Dipteran Larval DevelopmentDipteran Larval Development follows the follows the

progression of several stages of insect life on the progression of several stages of insect life on the bodybody

– Predictable, linear pattern of development (at Predictable, linear pattern of development (at optimum temperatures)optimum temperatures)

– Entomologist must identify all types of insects on Entomologist must identify all types of insects on body, temperature at crime scene over elapsed time, body, temperature at crime scene over elapsed time, what stages of life the specimen have already what stages of life the specimen have already completed, and any published data on species of completed, and any published data on species of insects relevant to case.insects relevant to case.

Determination of Elapsed Time Determination of Elapsed Time Since Death (cont’d)Since Death (cont’d)

• Method #2: Successional Method #2: Successional Colonization of BodyColonization of Body

– As a body decomposes, it attracts As a body decomposes, it attracts different insectsdifferent insects

– Entomologist identifies all species of Entomologist identifies all species of insects that have been present on body insects that have been present on body and reconstructs timeline.and reconstructs timeline.

Determining Whether the Body Determining Whether the Body Has Been MovedHas Been Moved

• Insects can lay eggs on body at original Insects can lay eggs on body at original scene and go unnoticed by killer.scene and go unnoticed by killer.

• Some insects live in only rural or urban Some insects live in only rural or urban settings, and their presence on body proves settings, and their presence on body proves body has been moved from original location.body has been moved from original location.

Body DisturbanceBody Disturbance

• Killers often return to body, and if body has been disturbed the insects have also been disturbed.

• Entomologists can time since death and when the body was disturbed

• Disturbance timeline can help link suspects back to crime.

Presence and Position of WoundsWounds

• Blow Flies lay eggs as close to wounds as possible on body.

• In advanced decomposition, atypical or irregular colonization patterns can indicate wound sites.

• Forensic Pathologist must be called in to identify a wound and what weapon caused it.

Linking Suspect to SceneLinking Suspect to Scene

• Based on Locard’s Principle of Based on Locard’s Principle of Exchange.Exchange.

• Criminals often take entomological Criminals often take entomological evidence from scene.evidence from scene.

• Types of insect bites on suspect can Types of insect bites on suspect can prove presence at certain location.prove presence at certain location.

• Insects found on suspect can carry Insects found on suspect can carry DNA or specific traits that match back DNA or specific traits that match back to insects on victim or crime scene.to insects on victim or crime scene.

DrugsDrugs

• Insects feeding on human tissue Insects feeding on human tissue absorb any unnatural substances like absorb any unnatural substances like drugs and poisons. drugs and poisons.

• If toxicology on victim does not work, If toxicology on victim does not work, analysis of insects can identify toxin.analysis of insects can identify toxin.

• Drugs can impact insect development Drugs can impact insect development by speeding it up or slowing it down.by speeding it up or slowing it down.

• Toxins digested by Blow Fly are Toxins digested by Blow Fly are retained through all life stages.retained through all life stages.

Human and Animal Neglect or Human and Animal Neglect or AbuseAbuse

• Insects living on a living human or Insects living on a living human or animal do no damage, but help to clean animal do no damage, but help to clean wounds.wounds.

• Presence of insects can show the Presence of insects can show the length of abuse or neglect.length of abuse or neglect.

• If insects colonized while victim was If insects colonized while victim was alive, it is difficult to tell after death.alive, it is difficult to tell after death.

Challenges to Forensic Challenges to Forensic EntomologyEntomology

• Temperature: Need temperature data to Temperature: Need temperature data to get a precise idea of insect get a precise idea of insect development speeddevelopment speed

• Season: Forensic entomology is only Season: Forensic entomology is only valuable during certain times of the valuable during certain times of the year, when insects are presentyear, when insects are present

• Exclusion of Insects: Freezing, burying Exclusion of Insects: Freezing, burying or wrapping a body can prevent insects or wrapping a body can prevent insects from colonizing it.from colonizing it.