Date of this Version
Death Scene Insect Succession in Nebraska: A Guidebook. Erin Bauer, Larry Barksdale, Emma Sidel, and Justine Laviolette. Lincoln, NE. 2022.
Insect behavior can be helpful to law enforcement in determining time of death, manner of death, location, and environment related to human or other animal victims found at a death scene. They may also provide clues about other aspects associated with an investigation (i.e., fly specks, suspect DNA). The study of how insects and related arthropods can aid in legal investigations is known as forensic entomology. Although this includes both civil applications, such as urban (i.e., maggots in mortuaries or insect structural damage) or stored product (i.e., illness from food contamination) entomology, this manual focuses on criminal applications, such as how insect evidence can be used at death scene investigations. One of the most important uses of entomological evidence for crime scene cases is in estimating time since death, or postmortem interval (PMI). Another related term, which is sometimes used interchangeably with PMI, and in other cases is used separately, is “time since colonization.” This is the time at which insects first colonize a dead body. Because blow flies visit a body often within minutes of death, it is reasonable that this would coincide with PMI. However, it is important to note that due to other factors such as temperature, location, weather conditions, and other variables, insect activity can accelerate or slow down and thus influence PMI. PMI can even be set back if animal predators find a corpse and feed on the flesh, inadvertently eating or destroying any insect eggs that have been laid on it. In this case, the earliest eggs to hatch on a body may be the offspring of insects that arrived later in the decomposition process rather than from initial insect visitors. If the body appears damaged by predator activity, the possibility of early colonizer larvae having been destroyed should be taken into consideration when making PMI estimations. The life stages of insects found on a corpse can give clues about how long the person has been dead and help build a timeline of the crime. While this guidebook will not be detailing how to calculate PMI, references are included at the end that will provide this information for law enforcement who may be doing this work. Investigators may also wish to consult a forensic entomologist specializing in this area for assistance. This guidebook discusses the general succession of forensically important insects expected to populate a decomposing body found in an outdoor environment during the summer months in Lincoln, Nebraska. There are limitations to generalizing this location with other locations. However, we are of the opinion that the information is useful for a general protocol for decomposition scenes be they murder, suicide, accidental, undetermined, natural, human, or non-human. This guide emphasizes what entomological evidence to look for at a death investigation, how to properly document evidence with photographs/temperature and humidity loggers/field notes, how to collect and preserve insect specimens, how to do preliminary analysis of insects and remains, how to decide whether to solicit an expert, and how to submit insect evidence for analysis. The more information and data that is available, the better it will be for an accurate and useful report. After a brief discussion about the history of forensic entomology, this manual is divided into several sections. The first section will examine the stages of decomposition and the types of insects that visit a corpse during these different decomposition stages. The second will provide detailed descriptions of some of the most common forensically important insect orders. The third section presents two field exercises as case studies illustrating the process of decomposition and insect behavior. The final section will examine the step by step process for collecting and preserving insects at a crime scene and the type of information that insect evidence can tell investigators. A references/resources list is available, as well as practice exercises to test your knowledge.