Forensic Entomology: History, Development, and Crime Scene Use

Introduction

As far as academic studies are concerned, the field of forensic entomology is relatively new in the West—but so, too, for that matter, is the field of criminology. Forensic entomology is a subset of criminology in that it focuses on the study of insects and arthropods and what they reveal about the death of a victim. This highly specialized science takes the field of entomology and combines it with the field of forensics, bringing together two very different but very useful bodies of knowledge that, when they intersect, provide valuable insights capable of helping investigators solve murders. This paper defines and discusses forensic entomology, examines its history and how it has developed over the years, and describes how entomology has affected the field of forensics, with case examples to illustrate these points.

History of Forensic Entomology

The history of forensic entomology begins, as far as historical records show, in China in the 13th century. It was there that Sung Tzu composed two works that touched on forensic entomology: Collected Cases of Injustice Rectified and Washing Away of Wrongs. The latter dealt with identifying the causes of death and how to examine a corpse for information. The former told the story of a peasant who slew his neighbor with a sickle and was identified by the murder weapon, which attracted flies drawn by traces of blood left on the blade that were invisible to the human eye (Rivers & Dahlem, 2014). The insects helped the authorities determine the murder weapon and the identity of the man to whom it belonged. This is the earliest known example of forensic entomology.

Other examples followed. In 17th-century Italy, Redi proved that maggots are not spontaneously generated in rotting meat but actually grow from flies (Rivers & Dahlem, 2014). Redi's proof prompted further investigation into the role of insects in the decomposition of flesh. This was followed in 19th-century France by Bergeret, who applied forensic entomology to an actual case for the first time in modern Western history. Bergeret used evidence of larvae and pupae to draw conclusions about the "mummified remains of a newborn baby" (Rivers & Dahlem, 2014, p. 18), making history with what is now recognized as the first modern instance of forensic entomology as it is practiced today.

In the 20th century, the field of entomology itself developed considerably, and as the world went to war there was ample opportunity to apply new entomological knowledge to the burgeoning field of forensics. Pest control was a major focus during both World War I and World War II, and by 1922 Karl Meixner had observed that the decomposition of bodies infested with maggots proceeded more quickly when the cadaver was that of a child than when it was that of an elderly person (Rivers & Dahlem, 2014). Hermann Merkel provided insights into how wounds to a body could alter the rate of decomposition by facilitating insect access. Josef Holzer investigated the effect of aquatic insects on submerged bodies—how certain species affected the skin in different ways and when caddisflies lay their larvae—which allowed him to estimate that a particular body had been underwater for seven days, based on the caddisfly larvae found on the cadaver.

These were just a few examples of investigators merging entomology with forensics. By the latter half of the 20th century, their work would begin to be studied in earnest by professionals in criminal justice, as forensics grew increasingly in demand and the need to determine cause and time of death placed forensic entomologists firmly on the map.

Development of Forensic Entomology

By the 1990s, three forms of forensic entomology had developed: urban forensic entomology, stored-product forensic entomology, and medicolegal forensic entomology. Medicolegal forensic entomology—the most commonly recognized form today—"deals with arthropod involvement in events surrounding felonies, usually violent crimes such as murder, suicide, and rape" as well as "other violations such as physical abuse and contraband trafficking" (Catts & Goff, 1992, p. 253). Urban forensic entomology addressed less sensational matters, such as lawsuits surrounding pests and arthropods in residences or the wrongful use of pesticides. Stored-product forensic entomology focused on commercial products that had been infested—such as maggots in candy bars or spiders in tissue paper (Catts & Goff, 1992). While each of these forms has application in modern law and criminal justice, the third form—also more accurately called mediocriminal forensic entomology—is the most widely applied.

It is this latter form that offers the greatest utility in crime scene investigations. As Joseph, Mathew, Sathyan, and Vargheese (2011) note, "by studying the insect population and the developing larval stages, forensic scientists can estimate the postmortem index, any change in position of the corpse as well as the cause of death" (p. 89). In other words, forensic entomology helps investigators better understand what happened, where it happened, when it happened, and how it happened when they are trying to piece together evidence in a murder, rape, trafficking incident, abuse case, or other crime in which insects and arthropods can help tell the story.

Knowing how insects and arthropods feed and nest is crucial, which is precisely why the field of entomology is necessary. Forensics would not be the same had entomologists not begun undertaking serious study of insects and arthropods in the 19th and 20th centuries. Their research helped others better understand the crimes of the modern era.

The development of entomology is especially critical for gauging the length of time a cadaver has remained in a specific location. Without forensic entomology, investigators would be limited to medical instruments and measures—such as examining the extent to which rigor mortis has set in, an approach helpful only for pinpointing time of death within one or two days of its occurrence. For cadavers discovered days or weeks after death, such medical measures are largely useless. Scientists who understand the role that insects and arthropods play in the decomposition process, however, can help stitch together the clues: "by calculating the age of immature insect stages feeding on a corpse and analyzing the necrophagous species present, postmortem intervals from the first day to several weeks can be estimated"—a far more robust approach to understanding the evidence than applying medical science alone (Amendt, Kretek, & Zehner, 2004, p. 51).

Conclusion

The field of forensics has benefitted substantially from the field of entomology—mainly because entomologists have obtained information about the natural world that is useful in understanding what happens to a body after it dies. The insects and arthropods of the world exhibit unique behaviors, with each species having its own relationship to death, allowing those who understand these behaviors to determine with a high degree of certainty the nature of death, the time of death, the place of death, and related circumstances. Entomology has thus merged with the field of forensics out of necessity, because it brings so much utility and insight for investigators.

Coupling the two disciplines makes sense today, just as it did nearly a thousand years ago in ancient China when the first historical record of forensic entomology was set down in writing. Since that time, ever-increasing attention has been paid to the natural world and to the behavior of insects and arthropods in particular. Because these creatures play a substantial role in the process of decomposition, they share in the story that crime scene investigators seek to reconstruct in their own pursuit of justice.