The effects of sharp-force thoracic trauma on the rate and pattern of decomposition in New England
Smith, Ashley Ciúine
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One of the most difficult tasks that a forensic pathologist or anthropologist is asked to accomplish is the determination of the postmortem interval (PMI) (Megyesi et al 2005; Ubelaker 1996). When soft tissue is still present, this interval is largely based on the extent of decomposition. Many factors, however, may alter the rate at which decomposition occurs including the temperature, humidity, insect activity, carnivore and rodent activity, and the depositional environment (Mann et al 1990; Sledzik 1997). In a 1990 study Mann et al determined that trauma was also a factor in decomposition, rating it a 4 out of a scale of 5 in importance. The results of the Mann et al (1990) study have been widely accepted by the field and today trauma is considered a major variable affecting the rate of decomposition in textbooks and other edited volumes (Byers 2011; Komar and Buikstra 2008; Sledzik 1997). In 2006, a study by J. A. Kelly, in South Africa, challenged the notion that trauma affects the rate of decomposition. In her dissertation, Kelly (2006) found that there was no significant difference in the rate of decomposition between traumatic groups and non-traumatic groups. In 2010, this research was further followed up by a team in the United Kingdom, specifically analyzing the effects of penetrative trauma on decomposition (Cross and Simmons 2010). Like the South African study, the authors discovered that there were no significant differences between a traumatic group and a non-trauma control (Cross and Simmons 2010; Kelly 2006). However, serious questions can be raised about these studies including the method of euthanasia, and the number of experimental subjects used (Cross and Simmons 2010; Kelly 2006). This present study utilized eight porcine carcasses to determine the effects of trauma on the rate and pattern of decomposition in the New England area. Three of the subjects were lacerated with a 15cm long incision penetrating in the thoracic cavity and three other subjects where lacerated with a 15cm long incision in the thoracic area but the incision did not penetrate into the cavity. A seventh set of remains was utilized as a control with an eighth used to verify the results. The subjects were placed on a surface depositional environment at the Boston University Research Facility in Holliston, MA from June to August 2011. Because factors such as temperature are so variable and can affect the temporal rate of decomposition, this study utilized the accumulated degree day (ADD) published in Megyesi et al (2005) as a measure of time. In addition, qualitative and semi-quantitative analyses were conducted, relying predominantly on the total body score (TBS) developed by Megyesi et al (2005). This system assesses a score, based on a stage of decomposition, for three specific regions of the body: head and neck, trunk, and limbs (Megyesi et al 2005). The sum of these scores is the total body score for a particular time. The present study assessed the TBS of all eight subjects and compared them on a temporal, ADD, and accumulated humidity day (AHD) bases. Following the experiment, a repeated measures analysis of variance (ANOVA) was conducted to determine if there was a statistical difference between the three subject groups. The results of this analysis revealed that there was no significant difference between the penetrated group, non-penetrated group, and control group. Trauma had no significant value in the rate of decomposition. A difference, however, was seen in the pattern of decomposition, with decomposition beginning at the wound site in traumatic groups and the facial region for the non-trauma group.
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