A BASIC algorithm for calculating the postmortem interval from arthropod successional data.

Abstract

A computer algorithm, implemented in the BASIC language, is presented for calculating the postmortem interval (PMI) from arthropod successional data. Entomology-assisted determination of the PMI promises to be a reliable technique in cases of homicide, suicide, accidental death, and unattended death due to natural causes. The program requires, as input, the identity of arthropod taxa recovered from human remains in a death scene investigation and machine-readable data on carrion-associated arthropod taxa and their known successional patterns of activity for the same geographical area. The program performs rapid comparisons of these lists and, on output, calculates an upper and lower estimate of the PMI, identifies the definitive taxa for these limits, and determines if the remaining corpse taxa have known successional patterns that are consistent for this estimate. An alternate output is provided if one or more corpse taxa do not overlap all the others at any single time in the succession. In that event, the user is prompted to recheck the identity of the non-overlapping taxon or taxa or reevaluate the environmental circumstances surrounding the case in question. Results of the analysis are saved to an ASCII file for output to a printer for making paper copies useful for the entomologist's Case Study Final Report. This program may make possible wider use of this technique in law enforcement and medical investigator offices that utilize both forensic entomologist expertise and IBM PCs (or compatible computers).