Limitations
The ultimate goal of forensic entomology is to get the most accurate post mortem estimate possible (Amendt et al., 2004). However there are some limitations which prevent this from happening.
Temperature data is a greatly variable environmental condition, which poses a difficulty to forensic entomology. There are several methods which can be used to determine the age of an insect found on a corpse, and all of them are dependent on the temperature of the body. One option is working out how far the insect is through its developmental cycle, calculated in degree days, which relates hatching time and temperature at time of death. The temperature used is determined after an examination of temperature at the crime scene, of the body, of the larvae present on the body, and compared with data from the nearest weather station. However accurate the methods may be in determining the temperature, because temperature can change unpredictably, there is the possibility of it causing error in determining the time of death. (Amendt et al., 2004). |
If the death being investigated was as a result of drugs, complications may arise in ascertaining the age of the necrophagous insects. Studies have found that drugs may influence insect development. Goff et al. concluded that Sarcophagidae (flesh fly) maggots feeding on a carcass developed faster when the deceased was killed by cocaine (Goff et al., 1989) or heroin (Goff et al., 1991). When determining the age of insects unaware of the presence of drugs, it is possible for the post-mortem interval to be underestimated by up to 24 hours (Bourel et al., 1999).
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There are still some necrophagous insects whose larval stages have not yet been sufficiently identified. One method used to identify a newly discovered larval stage on a cadaver is by DNA sequencing. DNA extraction from this organism is successful, however it must be compared to the DNA of museum specimens, the extraction of which is not so successful. This is because the chemicals used for the killing and storage of the insects interferes with the DNA. However the majority of necrophagous insects have been identified, and mitochondrial genome data for at least 400 species is available for use. (Amendt et al., 2004).
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Determining the time of death of a deceased is dependent on the lifestyles of the insect species found upon the body. Therefore there are many factors which may affect the accuracy of a forensic investigation. The conditions in which the body is located may limit its accessibility to insects, such as if it has been covered or is indoors, or if it is in the rain, resulting in a time period which cannot be accounted for through investigation of insects. There are also differences in insects’ developments and reproductive habits, such as what time of day different species of insects lay their eggs, presenting a possible misinterpretation of data. (Amendt et al., 2004).
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