Quantifying Statistical Uncertainty in Succession-Based Entomological Estimates of the Postmortem Interval in Death Scene Investigations: A Simulation Study

Timetables of carrion-arthropod succession provide critical baseline data for calculating entomology-based estimates of the postmortem interval (PMI) in cases of natural and untimely death; however, statistical confidence intervals typically do not accompany such estimates because of lack of methodology. Using 2 computer-intensive sampled randomization tests (the Jackknife and Bootstrap) and data from 3 studies of carrion-arthropod succession, we investigated the degree to which the PMIwidth (upper PMI limit - lower PMI limit + 1) was affected by missing taxa, corpse age, and taxonomic resolution of baseline data. Results generated from these methods were nearly identical. In each of the 3 studies, variability (uncertainty) in the PMIwidth increased as the number of missing taxa increased and as baseline data decreased in taxonomic resolution. In 8 of 9 other trials, the PMIwidth increased as corpse age increased and as the number of taxa (3, 6, and 9) used for the estimate decreased; in the exceptional case, the PMIwidth decreased with corpse age when 6 taxa were used. We conclude that randomization methods are potentially useful tools in forensic entomology both for conducting sensitivity analyses of arthropod successional data and for assessing statistical uncertainty of entomology-derived PMI estimates.