CASE HISTORIES OF THE USE OF INSECTS IN INVESTIGATIONS
Wayne D. Lord
Federal Bureau of Investigation, Washington, DC
INSECTS AND HUMAN DECOMPOSITION, Case 01
Human corpses, whether they have been produced naturally or as the result of foul play, are processed by insect decomposers in the same manner as any other piece of carrion. Forensic entomology, therefore, is based on the analysis of the insects and other invertebrates which sequentially colonize a corpse as decomposition progresses and on the rates at which the various stages of their offspring develop. Entomological information can be extremely useful in determining manner of death, movement of the corpse from one site to another, and length of the postmortem interval. The following case history studies are described to illustrate this use.
While a wide variety of insect species are attracted to decomposing remains and play an active role in the decay process, two groups, the flies (Diptera) and beetles (Coleoptera), are of major importance in most circumstances. Diptera, whose larvae are capable of living in a semi-liquid medium, are the first insects to be attracted to and to colonize decomposing remains. Fly larvae (maggots) are responsible for the dramatic consumption of the corpse's tissues. Only much later, when the corpse has to a large extent dried out, do species of other insect groups, notably beetles, move in and continue the process.
Case No. 1
On 4 June the partially clad body of a young female was found alongside a rural highway in the northwestern United States. An autopsy revealed that she had died of multiple head and neck wounds inflicted by a heavy sharp object. She was subsequently identified as a 14-year old prostitute. Her brother reported her as missing approximately four days prior to discovery of her corpse.
She had last been seen alive on the morning of 31 May in the company of a 30-year old army sergeant, the primary suspect. While considerable circumstantial evidence supported the theory that the victim had been murdered by the sergeant, an accurate estimation of time of death was crucial to establishing a possible link between the suspect and the victim at the time when death occurred.
Several estimates of postmortem interval were offered by medical examiners and investigators. These were based largely on the physical appearance of the body and the extent to which decompositional changes had occurred in various organs. They were not based on any quantitative scientific methodology.
Numerous fly larvae (maggots), adult flies, and other insects were observed and collected in and around the victim's wounds. Some were placed alive in small containers and subsequently reared to produce adult flies. Others were placed immediately into a liquid preservative. Additional specimens collected at the autopsy were processed in a similar manner. Numerous photographs of the crime scene, the surrounding vegetation and terrain, and the corpse were taken. These photographs included enlargements illustrating the adult flies and maggots present at the time the body was discovered.
Reports describing the condition of the body when found and detailing autopsy procedures and results also were reviewed. Climatological data, including maximum and minimum temperatures, incidence of rainfall, cloud cover, wind speed and direction, and relative humidity, were obtained from a government weather station located a short distance from where the victim was found. These data indicated the environmental conditions to which the remains and its insect associates were exposed.
Based on this total array of evidence, entomologists determined that the first insects to colonize the remains had arrived on 31 may. The insect evidence indicated a PMI of four days.
Based on this evidence, the army sergeant with whom the victim had been last seen alive was arrested and charged with first degree murder. On questioning he admitted to having murdered the victim by striking her six to eight times with a small hatchet sometime around noon on May 31. Subsequently, he entered a plea of guilty to the murder charge and was sentenced to life in prison without parole.
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