Forensic Entomology

History 101 Forensic entomology was first reported to have been used in 13th Century China (1235 murder by sickle) and was used sporadically in the 19th Century and the early part of the 20th Century, playing a part in some very major cases. However, in the last 15 years, forensic entomology has become more and more common in police investigations.

Forensic Entomology What is forensic entomology? –Forensic Entomology, or Medicocriminal Entomology, is the science of using insect and bugs as evidence.

After three days, insect evidence is often the most accurate and sometimes the only method of determining elapsed time since death.

Why Bugs? Insects and other bugs found on, in, or around a body can be used to determine: –Time of death –Cause of death –Location of death

Time of Death There are two main ways of using insects to determine elapsed time since death : –using successional waves of insects –using maggot age and development.

Using successional waves of insects Used when the corpse has been dead for between a month up to a year or more. Based on the fact that a human body supports a rapidly changing ecosystem going from the fresh state to dry bones in a matter of weeks or months. During this decomposition, the remains go through stages, and different stages of the decomposition are attractive to different species of insects.

Time of death using maggot age and development The theory behind estimating time of death, or rather the post mortem interval (PMI for short) with the help of insects are very simple: since insects arrive on the body soon after death, estimating the age of the insects will also lead to an estimation of the time of death.

EGGS Blow fly eggs are approximately 2 mm in length at 8 hours. During the first eight hours or so there is little sign of development. The egg stage typically lasts a day or so.

Larvae first instar --5 mm long after 1.8 days second instar mm long after 2.5 days third instar mm long after 4-5 days Identifying the correct instar stage is done based on size of larvae, the size of the larva's mouth parts, and morphology of the posterior spiracles. The time it takes to reach the different instars depends temperature and humidity.

Prepupae At the end of the third instar the larva becomes restless and starts to move away from the body. This prepupa is about 12 mm long and is seen 8-12 days after oviposition.

Pupa The prepupa gradually becomes a pupa, which darkens with age. The pupa which are about 9 mm in length are seen days after oviposition. The presence of empty puparia should therefore tell the forensic entomologist that the person in question has been dead more than 20 days.

Additional uses for bugs in forensics: –T–To determine : whether the body may have been moved after death whether the body may have been disturbed after death the presence and position of wounds the presence of drugs –T–To place a suspect at the scene of a crime –I–In civil cases

Location of Death After death, a succession of fungi, bacteria and animals will colonize the dead body. Leakage of fluids from the dead body will lead to the disappearance of certain insects, and other insects will increase as the time goes. A forensic entomologist can then estimate the time the body has been lying there by sampling the soil and insects underneath the dead body. If there is a difference in the estimates ( ie. the analysis of the soil suggests a short PMI, and the analysis of the body fauna suggests a longer PMI), one can suspect that the body has been moved.

The body may have been disturbed after death by the killer returning to the scene of the crime. This may disturb the insects cycle, and the entomologist may be able to determine not only the date of death, but also the date of the return of the killer.

Some times dead bodies are found in concealed environments, where blowflies have no access. If blowflies exist, it means that the body has been moved there.

The Presence of Drugs There is often not enough flesh left to determine drug presence, but maggots bioaccumulate so they can be analyzed to determine type of drug present. (like in CSI) Many of these chemicals influence the life-cycle of the maggot. Knowledge of drug use in the victim is therefore important not only in finding the death cause, but also in estimating the time of death.

The Presence and Position of Wounds Decomposition may obscure wounds. Insects colonize remains in a specific pattern, usually laying eggs first in the facial orifices, unless there are wounds, in which case they will colonize these first, then proceed down the body. If the maggot activity is centered away from the natural orifices, then it is likely that this is the site of a wound. For example, maggot activity on the palm of the hands indicates the probable presence of defense wounds.

Insects can be used to place a suspect at the scene of a crime. For instance, an insect inside a cocklebur was used to connect a rapist to the rape site.

Civil Cases child or senior abuse/neglect Some insects will colonize wounds or unclean areas on a living person. This is called cutaneous myiasis. In these cases, the victim is still alive, but maggot-infested. A forensic entomologist will be able to tell when the wound or abuse occurred. For instance, in the case of neglected children, the onset of maggot infestation will give a minimum time interval since the child last had a diaper change. Such cases occur particularly in young children and seniors.

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