Summary

Determination of colonization intervals of corpses ("post mortem interval") has been the major topic of forensic entomologists since the 19th century. The method is based on the connection of developmental stages of arthropods, especially of blow fly larvae, to their age. The major advantage against the standard methods for determination of early post mortem interval (by use of body temperature, body stiffness, post mortem lividities, chemical and electrical tests) is that arthropods can be an accurate measure even after the traditional methods fail, i.e., after approximately four to five days p.m..

Apart from estimating the colonization time, there are numerous other ways to use arthropod evidence. Recently, the proof of neglect of elderly persons and children, as well as artifacts produced by arthropods became a focus of interest. Therefore, this article deals with the broad range of possible applications of forensic entomology, including case examples and practical hints that relate to historical applications, DNA typing, blood spatter artifacts, estimation of post mortem interval (PMI), cases of neglect, and toxicology aided by arthropods as an investigative and criminalistic tool.

Key Words

Forensic Science, Blow flies, Beetles, Post Mortem Interval (PMI), Neglect of the Elderly, Neglect of Children, Case Reports, Decomposition, Toxicology



1. Introduction

Hundreds of arthropod species are attracted by corpses, primarily flies (Diptera), beetles (Coleoptera), and their larvae (fig. 1). The animals feed, live, or breed in and at the corpse, depending on their biological preferences, and on the state of decompostion (fig. 2).

Since arthropods are by far the largest and most important biological group on Earth (they outnumber even plants), they can be found in a wide variety of locations including many crime scenes. This opens a wide range of applications for forensic entomology, i.e., the use of mostly insects recovered from crime scenes, and corpses in an investigative or criminalistic context.

By calculating their developmental stage (fig. 3), arthropods are useful in estimating since when a corpse was inhabited by the animals. This estimate is often called the post mortem interval (PMI). Technically, this it is not a determination of PMI since the dead person may have been stored in an environment or under conditions that partially restricted access of insects (e.g., very cold, rainy, or tightly sealed environment). The term colonization interval is therefore more appropriate.

Especially insects are attracted to specific states of decomposition, e.g., bloated decay, fermentation, dried out tissue, or skeletonized corpses. Most species colonize a corpse for only a limited period of time. This change of insects over time is called faunal succession.

Together with the knowledge of mostly the larval growth rates (always depending on the specific environmental conditions), faunal evidence will provide an estimate of time since death, but only if the biological observations are set in relation to ecologic, criminalistic and medico-legal clues ([1-29]; see also following case examples).

There are several other types of information that can be derived from arthropods found at the scene of crime. For example, besides estimation of colonization time ("PMI"),

• suspects have been linked to the scene of crime as a result of them having been bitten by arthropods specific to the vicinity (fig. 11) ,
• insects which live in restricted areas but are found on a corpse in a different area can prove that the body was moved after death,
• blowfly larvae can give information on how long children or elderly people were neglected by their relatives or paid personnel (see 3.1.),
• hygienical aspects, e.g., appearance of larvae and flies in clean, empty rooms, or of "maggots" in food can be explained by linking the entomological findings to known death cases or other environmental factors from the surroundings of the scene [30,31],
• in former times, crime instruments were reported to be identified [32],
• drugs that cannot be determined any more from the decomposed tissue of the corpse can still be found in the insects that did feed from the corpse (see also 8.)
• the location of a stabbing wound can be determined by unusual feeding sites of beetles and maggots [e.g., 33],
• the question as to whether a person was killed and/or brought outside at night or at day, and/or while it was raining or not may be examined [34-38].