Forensic Entomology

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It was not until 1668 that Francesco Redi disproved this by observing how these creatures developed into flies, and much later, in 1894 that Megnin developed a method to link this process with a method for calculating the age of a dead body (Byrd and Castner, p. 41). Throughout the twentieth century scientific methods of analysis have improved greatly, with the result that at the present time forensic entomology is a well-established discipline within forensic science, complete with rigorous protocols and extensive underpinning research which help to ensure that it provides relevant, accurate and reliable evidence for crime investigation and prosecution purposes. Forensic entomology is therefore a dual discipline combining elements of natural science in the methods of collection and analysis of samples, and elements of criminology, in the interpretation and application of results, and in the preservation of evidence which is reliable enough to stand up to scrutiny in the criminal justice system. Although these two areas have a different focus, they are closely aligned in crime investigation procedures, requiring collaboration across disciplines according to clear scientific principles. This paper explores the contribution that forensic entomology makes to crime investigation and prosecution by examining three of its major areas of application: 1. Determining the post mortem interval (PMI). 2. Providing human DNA linkages and 3. Providing toxicology information. A number of limitations as well as legal and procedural issues are covered also in section 4. 1.Determining the Post Mortem Interval (PMI) through forensic entomology. 1.1 Species involved. Corpses provide a very specialized ephemeral environment which is colonized by particular communities of arthropods in a predictable manner, with one species following on after another in a process known as succession (Horswell, 2004, p. 347). The main species The first species to arrive, often within minutes of death, are blowflies. Blowflies from the Calliphoridae family are generally the first stage invaders, and then after these others follow Sarcophagids which constitute a second stage, often overlapping with the first stage somewhat. After this follow the third stage Muscids and Piophilids (Horswell, 2004, p. 348). 1.2 Types of information obtainable. Scientists are able to obtain good information from a corpse soon after death, by taking photographs, measuring temperature, observing rigor mortis and any wounds, and conducting various other tests on the tissue. With increasing passage of time, however, the tissue degenerates, and it is more difficult to obtain reliable data. Because the life cycle of insects is known, and the effects of temperature and weather can be factored in to the equation, careful collection of insects at the scene can provide useful estimate of the PMI. Empirical work in the laboratory has established standard growth times for many of the most common carrion feeding species, and this means that the determination of PMI has become the most used application of forensic entomology in modern crime scenes (Nabity et al. 2006, p. 1276). Another useful piece of information that can be obtained from examination of species present in a corpse is the whether or not the body has been moved.