Forensic entomology: applications and methods

Forensic

According to Elvidge (2014), the first record of the use of forensic entomology is Song Ci (Sung Tz'u), in 13th century China. However, using insects and arthropods like arachnids to aid in forensics investigations is a relatively new field, and one ripe with potential. The most notable applications of forensic entomology are in the identification of time elapsed since death, and the geographic location of death. When applying forensic entomology to homicide and other death studies, the specialist will take into account the various stages of decomposition. Forensic entomology can also be used to elucidate other types of crimes in which any type of decaying organic matter is a clue, in cases of human or animal abuse in which wounds have festered, in analyzing dried blood samples, in the investigation of botanical drug trafficking, and when detecting the presence of drugs in the deceased. Less glamorous but equally as significant applications of forensic entomology include investigating potential cases of food contamination, and aiding civil lawsuits involving human-insect interactions (Byrd, 2014). Forensic entomology may have even broader applications into crimes related to livestock. Because of the striking role insects and arthropods play in the global chain of life, entomology has tremendous potential to revolutionize forensics.

As Goff (2000) notes, "Anyone involved in death investigations quickly becomes aware of the connection between dead bodies and maggots," (p. 9). Although the largely invisible processes of bacterial decay and fugal growth occur prior even to the laying of eggs and the growth of maggots, maggots and grown insects like blow flies are often the first noticeable insects to appear on a dead body. This is why prior attempts at using insects in forensics have relied heavily on observable evidence such as the presence of flies. While investigating a murder, Sung Tz'u noticed that flies had been attracted to the sickle of only one farmer in the whole area. Sung Tz'u identified the farmer as the murderer, precisely because flies had been drawn to the bits of blood and decaying flesh still clinging to the farm tool (Goff, 2000). With modern technology and knowledge about insect behavior in the field of entomology, forensic scientists have at their disposal not just grown flies and arthropods like mites as their research assistants but also the precursors of these creatures.

Methods used in forensic entomology include collection of evidence at the scene of death or body recovery, including taking soil samples when possible. However, forensic entomologists may also need to sample the internal tissues of the body (Byrd, Lord, Wallace & Tomberlin, 2010). Deaths that take place in nature are the easiest to investigate because the forensic entomologist only needs to take samples from the ecosystem, whether it be forest, aquatic, or swamp, and piece together the puzzle as to when the death took place, as well as possible indicators of how and by whom. Unfortunately, most deaths do not happen as cleanly or as straightforward as this. Many take place in urban or suburban areas in which human development has encroached seriously and significantly on the indigenous ecosystems. Although endemic insect, bacteria, and fungal growth will remain present in local soils, the forensic entomologist needs to become familiar with patterns of insect behavior in human environments. As if this did not complicate matters enough for the forensic entomologist, the specialist must also investigate crimes that took place in geographic locations other than where the body was actually found. However, herein lies one of the strengths of the profession and where it can be applied most effectively. Insets and arthropods are relatively predictable creatures. The types of maggots that have nested, and the types of observable grown species can tell the story of where the murder actually took place, and not just where the body was found. Similarly, the life cycle of the insect and arthropod is predictable and can indicate the time of death based on the rate of decomposition. Factors like meteorology and geography will be factored into the forensic entomologist's toolkit of potential variables (Byrd & Castner, 2009).

Forensic entomologists need to be trained in both aspects of the profession: the entomology being the foundation of the research bolstered by its application to forensics science. Training and education parallels that of entomologists and forensic scientists, with great variation depending on areas of specialization and desire for mastery in the field.. Naturally, entomology research will entail some investigation into the role of insects and arthropods in the decay of bodies and organic matter. Because it is a science and has a set of highly reliable variables and data sets, the reputation of the field is strong and is only strengthening as computer modeling and other technological tools facilitate data collection and analysis.

Two surprising but understandable impediments to the work of the forensic entomologist include upper level predators like wasps and bees. Wasps and bees prey on some of the primary decomposition species like blowflies, and can therefore disrupt the investigation by disturbing the crime scene unwittingly (Elvidge, 2014). In some cases, insects have been known to drop traces of blood as they fly about their food. These traces of blood can confuse and confound investigations and render some of the data inaccurate and therefore inadmissible in court (Elvidge, 2014). More obvious forms of crime scene contamination can impede the progress of forensics investigations, as people will carry soil and insect species with them on their shoes and clothing. Therefore great care needs to be taken when working with forensic entomology as with any other branch of forensic science. To aid in the development of the profession, entomologists in research laboratories help forensic scientists collect evidence in a manner consistent with the law, analyze the evidence using state of the art tools, aid in identification of species and their behaviors, and likewise offer specialized training in order to bolster the profession and make it more viable in the future ("Forensic Entomology," n..d).

Insects at the fresh stage of composition tend to congregate in wound areas and natural orifices, and will be found in massive collections of eggs, larvae (maggots), pupae or pupal cases, and of course, adults (Anderson, n.d.). Collecting the evidence requires the preservation of each of these in a solution containing some rubbing alcohol, or anything designed to prevent their dehydration (Anderson, n.d.). As Anderson (n.d.) notes, when the only insect evidence is eggs, the live eggs must be observed every few hours to note when they first start hatching; this can indicate a rather accurate time of death.

The different stages of decomposition, which have been loosely grouped as "fresh, putrefaction, fermentation, dry decay and skeletonization," yield different organisms (SFU Museum of Archaeology and Ethnology, 2010). During early stages, immediately following death, the bacteria already present in the body consume its soft tissue, releasing gases including hydrogen sulphide, carbon dioxide, methane, ammonia, sulfur dioxide and hydrogen; insects are attracted to these "volatile molecules called apeneumones," (Joseph, Matthew, Sathyan & Vargheese, 2011, p. 89). The most eager insect feeders at the fresh stage are species of flies, especially blowfly species like Calliphora vicina, Calliphora vomitoria, and Cynomya cadaverina. These species feed off fluids from the freshly dead corpse, leaving more acidic tissues intact (SFU Museum of Archaeology and Ethnology, 2010). Weather conditions, as well as local variations in flora and fauna, will have a bearing on the nature, rate, and type of decay. This is why forensic entomology provides a thrilling puzzle that can be greatly aided by the use of computer modeling.