Estimating postmortem interval using RNA degradation and morphological changes in tooth pulp

In this study, time-dependent differences in RNA decay rates were examined to extend the time frame over which early PMI estimates can be made. Comparing the decay rates of a large, labile segment of β-actin RNA and a smaller, more stable, non-overlapping segment of the same RNA from tooth pulp, we were able to estimate PMI values of pigs buried within a shallow grave for up to 84 days. This compares favorably to an estimate of PMI using insect data. Full skeletonization and loss of insect activity was observed by day 28 of our study. In addition to differences in RNA decay rates, morphological changes were observed in the pulp as it aged postmortem. To provide a quantitative measure of progressive color changes, analysis of digital photographs of each tooth's pulp were used to construct a simple colorimetric assay. This assay was then used to cluster ages of pulp samples by color. The two assays, used in combination with one another, can create a more precise estimate of PMI. The potential advantages of this molecular means of estimating PMI include extending the time frame for such estimates, is applicable to samples collected worldwide (no specialized knowledge of local insect fauna is required), is relatively fast, and inexpensive.
Source: Forensic Science International - Category: Forensic Medicine Authors: Tags: Forensic Anthropology Population Data Source Type: research