The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Determination of the Postmortem Interval in Western Montana: A preliminary study on perimortem and postmortem characteristics in blunt force fractures


Anthropology, University of Montana

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Determining the postmortem interval is one of the most important and fundamental aspects surrounding a person’s death that a forensic anthropologist must determine. The goal of this experiment was to determine a transition point between those observed perimortem and postmortem features within the associated blunt force fractures. Approximately 130 deer bones were procured through a deer processer and were set out in the Montana environment for a total of 24 weeks. At one week intervals, five bones were broken by a 5 pound weight at a drop height of 2½ feet, after being weighed in order to account for moisture loss. Variables recorded were the fracture type, fracture angle, fracture line appearance, coloration of the fracture line, the presence of bone marrow, color of bone marrow and odor distinction. The first variable to exhibit a sign of postmortem change occurred at Week 12 (PMI= 77), where a rough appearance appeared at the fracture margins. Ultimately the bones showed complete postmortem characteristics after a PMI of 133 days. This study in comparison to others regarding the same context (e.g. Wheatley, 2008; Weiberg and Wescott, 2008), produce similar patterns regarding overall fracture types and fracture margin appearances, but differ in time frames. The results of this study shows bones determined to be perimortem or postmortem. However, it also shows bones that are in an intermediary stage with a mixture of both perimortem and postmortem fracture characteristics, which could ultimately represent a transition point between the two gross time frames.

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