Lipidic compounds found in soils surrounding human decomposing bodies and its use in forensic investigations - A narrative review.

Following decomposition of a human body, a variety of decomposition products, such as lipids, are released into the surrounding environment, e.g. soils. The long-lasting preservation in soils and their high diagnostic potential have been neglected in forensic research. Furthermore, little is known about the preservation, chemical transformation, or degradation of those human derived lipids in soils. To date, several studies identified various lipids such as long-chain free fatty acids and steroids in soils that contained decomposition fluids. Those lipids are preserved in soils over time and could serve as markers of human decomposition in forensic investigations, e.g. for estimating the post-mortem interval or identifying the burial location of a human body. Therefore, this review focuses on the current literature regarding fatty acid and steroid that have been detected in soils and associated with human body decomposition. After a short introduction about human decomposition processes, this review summarises fatty acid and steroid analysis applied in current case studies and studies related to taphonomic research. This review provides an overview of the available studies that have used fatty acids and steroids as identifiers of human decomposition fluid in soils in a forensic context and discusses the potential for developing this innovative field of research with direct application in a forensic context.

Ambrein: a minor, but common constituent of mammalian faeces?

For nearly 200 years, the only natural source of the alcohol ambrein has been coproliths produced in about 1% of sperm whales and in related jetsam. However, the finding of ambrein in adipocere/faeces of human corpses, led us to hypothesise that ambrein might occur in the faeces of other mammals. Herein, we used a recently developed gas chromatography-mass spectrometry method, with suitable derivatisation of the hindered hydroxy group of ambrein, to screen a number of extracts of mammalian faeces. Minor proportions of ambrein were detected in digested human sewage sludge and in the dung of elephant, domestic cattle, giraffe and buffalo. Whether ambrein formation in the terrestrial species is associated with coprolith formation, is unknown, but solid deposits known as enteroliths and fecaliths occur in humans and some domestic animals.

First evidence of terrestrial ambrein formation in human adipocere.

To date, the only known occurrence of ambrein, an important perfumery organic molecule, is in coproliths found in about one in a hundred sperm whales. Jetsam ambergris coproliths from the whale are also found occasionally on beaches worldwide. Here we report on the surprising occurrence of ambrein in human adipocere. Adipocere is a waxy substance formed post-mortem during incomplete anaerobic decomposition of soft tissues. Adipocere samples obtained from grave exhumations were analysed using gas chromatography-mass spectrometry (GC-MS). In addition to the typical fatty acids of adipocere, lesser amounts of ambrein were identified in the samples, in abundances similar to those of the major accompanying faecal steroids. The distribution of these compounds suggests that ambrein was produced post-mortem during the microbial decomposition of faecal residues and tissues. It is assumed that the adipocere matrix of saturated fatty acidsaided the preservation of ambrein over extended periods of time, because adipocere is stable against degradation. The association of ambrein formation in ageing faecal material, under moist, oxygen-depleted conditions, now requires more attention in studies of other mammalian and geological samples. Indeed, ambrein and its transformation products may be useful novel chemical indicators of aged faecal matter and decomposed bodies.

Investigation of sterols as potential biomarkers for the detection of pig (S. s. domesticus) decomposition fluid in soils.

This study was carried out to evaluate the potential of using cholesterol and coprostanol, as indicators for the detection of decomposition fluid of buried pigs (S. s. domesticus) in soils. In May 2007, four pig carcasses (∼35kg) were buried in shallow graves (∼40 cm depth) at the University of Ontario Institute of Technology in Canada. Two pigs were exhumed after three months (Pig 1, Pig 2) and six months (Pig 3, Pig 4) post burial. Soil samples were collected beneath the pig carcasses (∼40cm depth) and from grave walls (∼15-20 cm depth) as well as from a parallel control site. Coprostanol and cholesterol were extracted from soils, purified with solid phase extraction (SPE) and analysed with gas chromatography/mass spectrometry (GC/MS). A significant increase in cholesterol concentrations (p<0.05) and amounts of coprostanol were detected in soil located beneath the pig carcasses after three months of burial. It is assumed that during the putrefaction and liquefaction stages of decomposition pig fluid which contains cholesterol and coprostanol is released into the underlying soil. Therefore, cholesterol and coprostanol could be used as potential biomarkers to detect the presence of decomposition fluid three months after burial under comparable soil and environmental conditions. Further research is suggested for additional soil sampling before and after three months to investigate the abundance of these and other sterols.