title: Evaluating the utility of hexapod species for calculating a confidence interval about a succession based postmortem interval estimate.
abstract: Carrion insect succession patterns have long been used to estimate the postmortem interval (PMI) during a death investigation. However, no published carrion succession study included sufficient replication to calculate a confidence interval about a PMI estimate based on occurrence data. We exposed 53 pig carcasses (16±2.5 kg), near the likely minimum needed for such statistical analysis, at a site in north-central Indiana, USA, over three consecutive summer seasons. Insects and Collembola were sampled daily from each carcass for a total of 14 days, by this time each was skeletonized. The criteria for judging a life stage of a given species to be potentially useful for succession-based PMI estimation were (1) nonreoccurrence (observed during a single period of presence on a corpse), and (2) found in a sufficiently large proportion of carcasses to support a PMI confidence interval. For this data set that proportion threshold is 45/53. Of the 266 species collected and identified, none was nonreoccuring in that each showed at least a gap of one day on a single carcass. If the definition of nonreoccurrence is relaxed to include such a single one-day gap the larval forms of Necrophilaamericana, Fanniascalaris, Cochliomyia macellaria, Phormiaregina, and Luciliaillustris satisfied these two criteria. Adults of Creophilus maxillosus, Necrobiaruficollis, and Necrodessurinamensis were common and showed only a few, single-day gaps in occurrence. C.maxillosus, P.regina, and L.illustris displayed exceptional forensic utility in that they were observed on every carcass. Although these observations were made at a single site during one season of the year, the species we found to be useful have large geographic ranges. We suggest that future carrion insect succession research focus only on a limited set of species with high potential forensic utility so as to reduce sample effort per carcass and thereby enable increased experimental replication.
authors.affiliation: Department of Biology, West Virginia University, 53 Campus Drive, Morgantown, WV 26505, United States. Electronic address: anicho16@mix.wvu.edu.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Perez
authors.affiliation: Department of Biology, Saint Joseph's College, 1498 S College Ave, Rensselaer, IN 47978, United States. Electronic address: blowfly@technologist.com.
authors.forename: Neal H
authors.initials: NH
authors.lastname: Haskell
authors.affiliation: Department of Biological Sciences and International Forensic Research Institute, Florida International University, 11200 SW 8th Street, Miami, FL 33199, United States. Electronic address: jedwell@fiu.edu.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Wells
mesh_terms: D000818:Animals; D001517:Coleoptera; D016001:Confidence Intervals; D004175:Diptera; D004772:Entomology; D005247:Feeding Behavior; D049429:Forensic Pathology; D006801:Humans; D007814:Larva; D011180:Postmortem Changes; D013552:Swine
keywords: Confidence interval; Forensic entomology; Occurrence; Postmortem interval; Statistics; Succession