In a homicide case or any accident that results in death, it is essential to know the exact time and place where the death occurred. Insects and their larvae may yield elaborate data, such as the amount of time that has elapsed after death, whether the body has been moved to another site, or whether the body has been disturbed by the killer after returning to the crime scene. The study of insect evidence in criminology is called “forensic entomology.”
The earliest records belong to ancient China. In 1235 Sung Tz'u, a Chinese “death investigator,” wrote a book entitled The Washing Away of Wrongs (translated by McKnight, 1981) in which what was known in forensic science at that time was detailed. In this text, an actual forensic entomology case was recounted, with the best known historic case being given. A murder had been committed in a little village in China. A man had been hacked to death with a rice-harvesting sickle. Because the village was one where rice was grown, everyone possessed a sickle, which meant that there were therefore many suspects. A professor at UC Davis, Robert Kimsey, explains how the murderer was caught; “The local magistrate very cleverly lined up every one of the farmers with their sickles out in the field. He walked up and down the line and pointed to the man who had committed the murder. The evidence he used to identify this man as a murderer-who later confessed, by the way-was the fact that green bottle flies were attracted to this man's sickle. And nobody else, of course, had green bottle flies on their sickle because the flies were only attracted to a surface that had blood on it. No matter how rigorously you cleaned your sickle, you would still have remnants which these flies would be able to detect.”
Since those times, forensic entomology has made great progress. The way insect evidence helps justice works through the successive colonization of a corpse by a predictable succession of arthropod species. Different types of insects start coming right after death occurs. Organic remains, like flesh, blood, waste material, bone marrow, and hairs all attract certain types of insects. Owing to the time difference between the decaying body parts, the flies arrive at different times. They consume the parts that are nutritious for them and leave the body for another group.
As a manifestation of the divine name Quddus (the All-Holy), dead bodies decompose and nature is kept clean. Thus, the process started by microorganisms is made faster by the insects. Blow flies are among the first group of workers in this respect, whereas the dermestids, for instance, do their duty in the later stages of decomposition. The larvae of dermestids are not found before the body dry outs. The larvae and adults feed on dry skin and hair, as well as other dry dead organic animal matter. Dermestids are a common pest in homes, as well as being undesirable in insect collections and taxidermists collections at museums.
The first month after death is the most effective time for the application of forensic entomology. When death takes place, the insects start to arrive within minutes. However, it should be noted that insect evidence does not always tell us about the exact time of death. But at least we can infer that death occurred at a time that is greater than the age of the larvae that are developed in the body. If we have sound knowledge about the life cycles of the relevant insects, we can make more accurate predictions.
Another thing entomology helps us find out is the location of a murder. Sometimes a victim is moved after a murder in order to get rid of important evidence. For instance, a victim can be taken to a mountainous area after being killed in a town at low altitude. Entomologists can tell you about the habitat of the insects found on the body and give one a good idea about where the murder took place. Many insects live in very special geographical conditions. The altitude, temperature, and vegetation all affect the types of insects that live in the area. Furthermore, a meticulous entomological study will tell you whether the body has been, moved, the season in which it was killed, and whether the murder was committed indoors or outdoors.
Entomologists even help forensic experts with the cause of death. Particularly when the body has already decayed, it can be difficult for the police to determine the cause of death. In normal conditions, insects lay their eggs in certain parts of a body. If there are open wounds however, they will also lay their eggs there. So, if any eggs are found in unusual spots they indicate a probable wound.
When a murder or suicide is suspected to have resulted due to poisoning and if the body is decomposed, toxicological analyses that are made on the insects or the larvae taken from the body can help.
Bergeret (1855), who resided near Paris was the first westerner to use insects as forensic indicators. The body of a baby was found behind the plaster mantle in a house, and an investigation was begun. Bergeret determined that the assemblage of insects associated with the corpse pointed to a state of decay that dated back several years; consequently, the question of guilt was thrown upon the earlier occupants of the house, and not upon the current ones.
Case histories have documented the utility of medicocriminal entomology and point out the unique contributions that this field of science has made. Nuorteva et al. (1967, 1974) presented a series of cases from Finland in which blow flies were used as indicators for indoor as well as outdoor death scenes, and where the immature (larval) or adult stages were used for identification. Leclercq (1969) provided a typical case scenario and outlined how insect data were used to corroborate information obtained from other sources. Bernard Greenberg (1985) outlined several cases, including a description of how laboratory fly-rearing data were used to calculate the number of accumulated degree hours (ADH) required for certain blow fly species to develop, and how such data were applied to the solution of a murder case in Illinois. In another recent case, Greenberg described how the absence of insects in a seemingly straightforward death scene led to a killer's confession. A window next to the victim had been open when the body was found, thus giving the impression that the murderer had forced entry into the room the night before. However, the air conditioned room was cool, even though it was very hot outdoors. In reality, the killer was known to the victim, had a key, and had returned to “set the stage,” opening the window just prior to feigning discovery of the corpse. The insects thus had insufficient time to colonize the body as the window had been closed prior to the return of the killer. When confronted by this biological reality as pointed out by medicocriminal entomology, the killer confessed.
A Hungarian ferry skipper had been condemned to life imprisonment for the murder of a postmaster, whose stabbed body had been found one evening in September on the ferry. The ferry skipper had arrived at 18:00 that day, and the body of the murdered postmaster had been found some hours later. The autopsy was performed the next day at 16:00. Masses of yellowish fly eggs and numerous newly hatched larvae of 1 to 2 mm in length were present, and the findings were recorded in the autopsy report. No attention was paid to this observation at the trial, however. On assumed evidence, the ferry skipper was condemned to life imprisonment in spite of his swearing that he was innocent. Eight years later the case was reopened. At the new trial, Dr. Mihalyi pointed out that no sarcophagous flies are active in Hungary after 18:00 in the month of September. He also recalled some of his experiments indicating that, at a temperature of 26 degrees Celsius, the yellowish eggs of Lucilia caesar (L.) hatch after 13 hours, those of L. sericata (Meigen) hatch after 10-11 hours, and those of Phormia terranovae Robineau-Desvoidy 14-16 hours after oviposition. These data, when applied to the case of the ferry skipper, led to the conclusion that it was not possible for the eggs to have hatched if they had been laid during the day the autopsy was performed, and that they must have been laid during the previous day before 18:00, since the flies are not active after this time. Dr. Mihalyi's data on oviposition was verified and, on the basis of this and other evidence, the ferry skipper was released from prison.
Entomology, along with other sciences whisper in our ear that in “the Book of the Universe” there are different signs that lead us to the truth; they are there for us to use if we search for them and fulfill the requirement of causes. This is when the world will open its mysteries to us.
- The illustration is taken from the poster of the annual Insect Fear Film Festival at the University of Illinois, Feb. 2005.