Forensic Entomology

Forensic Entomology

Introduction

The application of the study of arthropods such as flies and beetles to legal proceedings, are both criminal and civil. Arthropods are animals with jointed legs and include insects, arachnids (spiders), centipedes, millipedes, and crustaceans. Forensic entomology, principally related to insects, has become a common tool in death investigation, in assigning a time since death occurred (postmortem interval [PMI]), and/or for determining a site of death. Death and criminal investigations are broadly categorized as medicocriminal/medicolegal entomology, while medical entomology is the subdiscipline that deals with insects that can affect human health and carry disease such as mosquitoes and ticks. Forensic entomologists can also be involved in legal proceedings classified as urban entomology (involving insects such as cockroaches), and stored product entomology, which includes infamous cases (or allegations) of insects and insect parts in fast food (Amend, 2007).

Flies and beetles are the insects used most often to determine time or place of death. The entomologist studies the types of insects present at a death scene, their number, and stages of the life cycles that are observed. Techniques known as insect succession are of particular value for determining the PMI, since different species will be attracted to the body depending on the stage of decomposition. The entomological analysis of a death scene involves studies and observations at the site as well as in the lab. At a death or crime scene, the entomologist must study the area around the body carefully, take measurements of critical variables such as temperature and sun exposure, document and photograph, and obtain samples with as little disturbance as possible. Normally, samples from the body itself are taken during autopsy. In the lab, insects collected at the site are studied and often are raised through their life cycle. This allows for definitive identifications that can be difficult at earlier stages in the life cycle and can improve the estimate of the PMI. Rearing the insects also provides the entomologist with information and data that may be useful in future casework (Timmermans, 2006).

Temperature is critical in determining what types of insects will appear at a death scene and how quickly they will develop. Other factors are the season, how much sun exposure the scene gets, what time of day the body was placed at the scene (time of day determines which types of insects will be active), whether the body was buried and, if so, how deeply, how the victim is clothed or wrapped, and whether the scene is in an urban or rural environment. Scavengers also can be an issue. Conversely, insect damage to a body may look like trauma, injury, or burns, and the forensic entomologist can be invaluable in distinguishing this kind of postmortem damage from injuries that might have contributed to death. Finally, insects that feed on or move through bloodstains at a scene can create patterns that may be difficult to interpret. Insects that have fed on blood can leave droppings that often look like bloodstain patterns (Thomas, ...