Degradação do DNA de Raízes de Cabelos em Água do Mar - Contributo para a Estimativa do Intervalo Post Mortem e Identificação Genética do Cadáver

Abstract

The time that elapses between the moment of the individual's death and the discovery of his corpse corresponds to the Post Mortem Interval (PMI). Determining this range is extremely relevant to Forensic Sciences, especially in the areas of Forensic Anthropology and Pathology. Theoretically, through observation and interpretation of the various post mortem cadaveric phenomena, it is possible to estimate the PMI in an approximate way. However, there is no method that can accurately define the exact moment of a person's death, which makes the study of PMI a scientific challenge to be solved. During this study, the need for more alternatives to estimate the PMI was evident, especially of methodologies that could be applied to the calculation of longer post mortem intervals, using biological materials that are less susceptible to fast deterioration, i.e. hairs. The slow degradation capacity of this biological material is considered an advantage when compared to fast decomposition of organs and other soft tissues, especially in cases of cadaveric samples with longer post-mortem intervals that were exposed to environmental factors for a longer period of time. Therefore, the study of the amount and degradation level of hair DNA, as well as the possibility of obtaining a complete genetic profiles through genetic markers analysis, such as STR, are important and can contribute to the estimation of PMI. Since the amount and degradation of hair root DNA are directly related to the environmental factors of the place where the hairs were exposed and with the time of this exposure, it is important to perform studies in which these factors can be simulated in a controlled manner. Therefore, the study was proceeded in hairs that were exposed to seawater. To perform the study, a scalp fragment was collected and divided into 2 fragments, one submitted to partial immersion and the other submitted to total immersion in seawater during 17 days. Hairs from these two fragments were collected daily. During the experimental procedure, laboratory and statistical analyzes were performed to investigate the existence or absence of a significant correlation between the amount and degradation level of the cadaver hairs' DNA and the time elapsed after death. The main objective of this work, based on the analysis of the amount and degradation level of hair DNA submerged in seawater, was to investigate the possibility of using this methodology as an alternative method capable of estimating the post mortem interval, as well as allowing the cadaver genetic identification. In the end of this project, it was possible to comprehend the potential of DNA analysis of cadavers' hair submerged in seawater to be used as an alternative tool in the post mortem interval estimation and in the identification of individuals, in case of longer periods of time when compared to methods that use organs and other soft tissues for analysis. Therefore, this method of analysis seems promising for future research in the area of Forensic Science. However, it is recommended a larger amount of sampling in order to improve the accuracy of the method.