Using Mummification and Temperature to Estimate Postmortem Interval

Mummification is an alternative to human decomposition that involves desiccation of the tissues of the body, particularly the skin. A total of 44 decedents with known postmortem intervals (PMIs) were collected from the Maricopa County Medical Examiner's Office and given a cumulative mummification score (CMS) describing the extent of their mummification using a novel scale. PMI was multiplied by the ambient temperature of the scene to allow for the creation of a new variable, accumulated degree days (ADDs). A non-linear relationship was found between PMI and ADD. The variables were transformed to generate a linear relationship. Pearson correlations and regression analyses were performed and generated a final graphical model (p < 0.05, r = 0.750, n = 34). An equation was calculated based off of a previously-established protocol that produced a range of possible PMIs from a given CMS. The accuracy of the ranges the equation provided was not very high (14%). When expanded to the 95% confidence intervals, 41% of cases fell within the predicted range. The data collected may not have been accurate due to the method of PMI calculation. The PMIs were calculated from the time the decedent was last known alive, which was likely artificially high as many of the individuals were socially isolated premortem. There were also several confounding variables that were not accounted for. Any variable that prevented or accelerated the escape of water from the body's tissues would slow down or speed up mummification, respectively, including clothing, skin-skin or skin-surface contact, position, body mass, humidity, and airflow. Ideally, this study would be performed with decedents with known PMIs who were tracked longitudinally.