Development of an analytical chemistry method to assess the postmortem interval

Recently, there has been a push within the forensic science community to develop more quantitative methods to better estimate the time since death or postmortem index (PMI) in decomposing remains found on crime scenes. When quantification is necessary, scientists often use gas chromatography/mass spectroscopy (GC/MS), as it can simultaneously separate complex mixtures to identify and quantify the compounds present. Previous research has indicated that byproducts from putrefactive processes in liver and brain tissue could be detected and quantified using GC/MS methods.1, 2 During human decomposition, bacteria decarboxylate various amino acids present in the body, including ornithine and lysine. The products are two diamines known as cadaverine (CAD) and putrescine (PUT). Another biogenic amine produced in a variety of reactions during decomposition is methylamine (MEA). Establishing a reliable trend between the concentration of these three amines (CAD, PUT, and MEA) and the PMI would be incredibly valuable for death investigations. Extraction of the biogenic amines from muscle and liver tissues, followed by derivatization with pentafluorobenzaldehyde (PFB), is required before GC/MS identification and quantification. Using two internal standards, hexanediamine (HXD) and pentafluoroaniliine (PFA), external calibration curves of the derivatized biogenic amines were used to quantify the MEA, PUT, and CAD. Preliminary results indicate that this method could be reliable for estimating PMI during early decomposition stages. Finally, using accumulated degree days (ADD)—a function of time and cumulative temperature exposure—may also contribute to improved PMI estimation and forensic analysis of death scenes.   References: 1. Balta, J. Y.; Blom, G.; Davidson, A.; Perrault, K.; Cryan, J. F.; O’Mahony, S. M.; Cassella, J. P. Developing a Quantitative Method to Assess the Decomposition of Embalmed Human Cadavers. Forensic Chem. 2020, 18 (100235). DOI: 10.1016/j.forc.2020.100235 2. Pelletti, G.; Garagnani, M.; Barone, R.; Boscolo-Berto, R.; Rossi, F.; Morotti, A.; Rof, R.; Fais, P.; Pelotti, S. Validation and Preliminary Application of a GC–MS Method for the Determination of Putrescine and Cadaverine in the Human Brain: A Promising Technique for PMI Estimation. Forensic Sci. Int. 2019, 297, 221−227. DOI: 10.1016/j.forsciint.2019.01.025