LABORATORY DETECTION LIMITS OF POTENTIAL HUMAN DECOMPOSITION PRODUCTS UNDER A VARIETY OF SOIL CONDITIONS

This study presents research to support development of a spectroscopic probe that could be used to detect clandestine human burials in a forensic context. The specific aim of this study is to determine the laboratory infrared spectroscopic detection limits for four human decomposition products (palmitic acid, oleic acid, leucine, and calcium pyrophosphate) in a range of soil particle size and organic matter content conditions and whether the compounds can be detected using laboratory scans of samples taken from two human burial analogue sites.

Known concentrations of four potential human decomposition products were added to soil samples ranging over a variety of soil particle size and organic matter content. The soil samples were scanned using FTIR (Fourier transform infrared spectroscopy) and detection limits were calculated. In order to demonstrate the applicability of this method to field conditions, samples from cores taken from two pig carcasses, used as human burial analogues, were scanned using the same methods. The pig carcasses had been buried for about nine months when the cores were obtained.

The minimum detection limit for palmitic and oleic acid was determined to be 0.1%, 0.05%, and 0.01% in soil samples of sandy, silty, and clayey particle size, respectively. In samples of known concentration, lower levels of palmitic acid and oleic acid were detectable in samples with smaller particle size and higher organic matter content. This suggests that human decomposition products containing fatty acids will most readily be detected in soil conditions consisting of smaller particle size and higher organic matter content. Peaks suggesting the presence of a fatty acid (either palmitic acid or oleic acid) were present in scans from some of the samples from the pig burial site, but the spectra did not indicate the presence of the other two decomposition products.