Measuring desiccation: A system using bioelectrical impedance analysis

As submitted by the proposer: This project will result in improved methods for understanding desiccation, describing and measuring tissue on human remains at a crime scene and estimating post-mortem interval (PMI). The project helps to improve tools for examining tissue, which may otherwise be considered too desiccated to provide useful data for post-mortem interval estimation. This project will (1) develop an ordinal level measures of desiccation – a total body desiccation score, and (2) use bioelectrical impedance analysis to measure post-mortem changes. These objectives are addressed in a two-year research project. Human donors are placed in an outdoor facility in an arid high-altitude desert. Twenty-one human donations have been placed to date and all have desiccated. The standard taphonomic pathway as described by Megyesi et al (2005) leads to skeletonization. In arid areas, an alternate taphonomic pathway sometimes occurs through desiccation that slows decomposition. This pathway can result in the mummification of part of the remains with moist decomposition ongoing in part of the remains (Parks 2011, Galloway et al. 1989). The remains continue to change, but in ways not scored on the total body score (TBS). The existing TBS will be modified to better reflect the desiccation pathway in a total body desiccation score (TBDS). This project also uses bioelectrical impedance analysis techniques to measure postmortem changes. Resistance measurements are based on the composition of the extracellular fluid, while reactance measures the ability of cell membranes to act as capacitors. Based on the bioelectrical properties of tissue, postmortem changes in cellular structure and the composition of the extracellular fluid can be measured using bioelectrical impedance analysis. Querido (2002) has shown strong correlation between electrical impedance of the intact abdomen and PMI in rats. Preliminary results on human bodies are promising. Expected products include quarterly reports over the course of the two years and a final report, each meeting NIJ requirements. In addition, a body of raw data will be archived, and available to researchers. The results will be disseminated to scholars through a series of papers and presentations, and to practitioners through workshops at regional meetings at FIRS. If successful, the principal investigators will also present a workshop at the American Academy of Forensic Sciences on the bioelectrical impedance equipment and analysis. The workshops will include suggestions for “best practices” for dealing with desiccated remains. Improved scoring systems for desiccated remains will help to increase the reliability of PMI estimates. This project contains a research and/or development component, as defined in applicable law. ca/ncf