Abstract
Criminal investigations of suspected murder cases require estimating the post-mortem interval (PMI, or time after death) which is challenging for long PMIs. Here we present the case of human remains found in a Swiss forest. We have used a multidisciplinary approach involving the analysis of bones and soil samples collected beneath the remains of the head, upper and lower body and “control” samples taken a few meters away. We analysed soil chemical characteristics, mites and nematodes (by microscopy) and micro-eukaryotes (by Illumina high throughput sequencing). The PMI estimate on hair 14C-data via bomb peak radiocarbon dating gave a time range of 1 to 3 years before the discovery of the remains. Cluster analyses for soil chemical constituents, nematodes, mites and micro-eukaryotes revealed two clusters 1) head and upper body and 2) lower body and controls. From mite evidence, we conclude that the body was probably brought to the site after death. However, chemical analyses, nematode community analyses and the analyses of micro-eukaryotes indicate that decomposition took place at least partly on site. This study illustrates the usefulness of combining several lines of evidence for the study of homicide cases to better calibrate PMI inference tools.
Highlights
The estimation of a post-mortem interval (PMI) or the time since death has been a research priority in forensic science for over a century since the pioneering work of Mégnin[1] (1894), who defined the decomposition stages of corpses for the first time
Discovery of old decomposed human corpses is a reality and new methods are required for long PMI estimations
While the relevance of mites for criminal investigations is well-established[27,30], studies of other potential forensic indicators are still rare and comparative studies are lacking. Soil arthropods such as springtails (Collembola)[28,29] and ants[33] were proven useful for PMI estimation
Summary
The estimation of a post-mortem interval (PMI) or the time since death has been a research priority in forensic science for over a century since the pioneering work of Mégnin[1] (1894), who defined the decomposition stages of corpses for the first time. A still limited, but increasing number of studies have focused on the effects of cadaver decomposition on the underlying soil as new venues for gathering forensic evidence. These studies monitored the changes in soil chemistry[13,14,15,16] and the community structure of soil micro-organisms[17,18], bacteria[19,20,21], fungi[20,22,23], testate amoebae[24,25], nematodes[26] and micro-arthropods[27,28,29,30,31,32]. Some details about the finding must be kept under nondisclosure
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