Forensic entomology is the study of insects for the purpose of obtaining evidence that can be used in legal proceedings. A forensic entomologist will examine such factors as insect species succession, larval weight, larval length, and accumulated degree days of insects – in simple terms, the amount of time it takes for insects to proceed from larva to maturity under the known weather conditions – to draw conclusions about a crime scene or other investigation.
As technology has advances, the type of information available through forensic entomology has expanded. If an insect has consumed human blood, it may be possible to use DNA analysis of the consumed blood to connect a victim to a crime scene where the insect was found. It may be possible to perform a toxicology screening on insects found on a skeletonized corpse in order to determine any medications or other chemical substances that the victim consumed prior to death.
Legal matters that may rely upon the work of a forensic entomologist include:
- Crime Scene Investigation - Forensic entomology may be useful at a crime scene, particularly in a suspicious death or homicide case, to help determine the time of death. The presence of insects, the types of insects found and their stage of development, may shed significant light on how long a person has been deceased, even after considerable decay. The presence of certain insects, or evidence that the insect's reproductive cycle has been disturbed, may indicate that a body or other evidence was moved from another location.
- Abuse and Neglect Investigation - The presence of insects on children or persons living in institutional settings may constitute clear evidence of neglect, or in some cases of deliberate abuse.
- Accident Cases - In some collision cases, including car accidents and airplane accidents, it may be possible for a forensic entomologist to determine that an insect – particularly a stinging insect – was present in the vehicle, potentially creating a distraction that led to the accident.
- Insect Infestation - A forensic entomologist may be able to identify the origin of an insect infestation, as well as the sufficiency or appropriateness of pesticides and other treatments meant to prevent infestation or exterminate the insects.
- Food Contamination - Where insects are found in stored food, it may be possible for a forensic entomologist to identify where the insect infestation occurred by examining the insect species and life cycle stages, potentially determining if the contamination occurred at the point of manufacture, during shipment or distribution, at a retailer, or at the location of the buyer or end-user.
Although forensic entomology may produce a great deal of useful information, the following limitations should be kept in mind:
Weather Sensitivity - Insects will vary in number depending upon the weather and time of year. Fewer insects will be present in the winter than in summer months.
Reliance on Weather Data - Although weather data may be used to control for some of the weather effects on insect species and numbers, the data will typically come from weather centers that are in a considerably different location than the location of the investigation, and local variations in weather patterns can have a significant effect on insects.
Delays in Obtaining Results - If it is necessary to breed insects found at the scene of an investigation, a considerable amount of time may pass before the breeding is complete.
Treatment of the Evidence - Insect activity can be affected by the manner in which evidence is treated, including burial, wrapping, chemical exposure, or freezing, potentially complicating a forensic evaluation of insect data or rendering its findings unreliable.