Flow cytometric evaluation of DNA degradation: a predictor of postmortem interval?

The time of death of an individual can easily be determined if the postmortem interval can be assessed. Although livor mortis, rigor mortis, and, to a lesser degree, algor mortis have been used to estimate the postmortem interval, most experienced forensic pathologists agree that these characteristics provide, at best, "postmortem windows." Quantitation of the vitreous fluid potassium level has been of some value in evaluating the early postmortem interval, but the accuracy of this method is dependent on external conditions, the availability of vitreous fluid (e.g., burned bodies, head trauma), and the purity of the sample. A simple, relatively inexpensive assay performed on readily available tissues, less dependent upon external factors, and providing data that could be plotted on a reproducible control curve would be of value in determining the postmortem interval accurately. This office is currently investigating flow cytometric DNA content analysis performed on splenic tissue harvested from a series of autopsies with known postmortem intervals. Preliminary data suggest that DNA degradation occurs in a predictable pattern over the intermediate postmortem period. A graph is being generated that will plot the degree of DNA fragmentation with respect to the postmortem interval. It is hoped that sections of spleen from "unknown" cases could be submitted for flow cytometric analysis of DNA content and plotted on the curve to estimate the postmortem interval and, thus, determine the time of death.