Postmortem interval

Most methods are based on the measurement of physical and chemical changes that occur to a body after death. However, most of these changes are influenced by different variables (e.g., external temperature, physical activity immediately before death, etc.) that make the correlation between a measured variable and postmortem interval (PMI) rather inaccurate. 

Laywell, E.D., Kukekov, V.G., Steindler, D.A. (1999). Multipotent neurospheres can be derived from forebrain subependymal zone and spinal cord of adult mice after protracted postmortem intervals. Exp Neurol, 156, 430-33. 

Megyesi, M. S., Nawrocki, S. P., and Haskell, N. H. (2005). Using accumulated degree-days to estimate the postmortem interval from decomposed human remains. /. Forensic Sci. 50, 618-626. 

Goff, M. L. (1992). Problems in estimation of postmortem interval resulting from wrapping of the corpse A case study from Hawaii. /. Agri. Entomol. 9, 237-243. 

Love, J. C. and Marks, M. K. (2002). Taphonomy and time, estimating the postmortem interval, in Hard Evidence Case Studies in Forensic Anthropology (D. W. Steadman, Ed.). Upper Saddle River, NJ Prentice Hall, 160-175. 

Sabucedo, A. J. and Furton, K. G. (2003). Estimation of postmortem interval using the protein marker cardiac Troponin I. Forensic Sci. Int. 134,11-16. 

Wells, J. D. and Lamotte, L. R. (2001). Estimating the postmortem interval, in Forensic Entomology The Utility of Arthropods in Legal Investigations (J. H. Byrd and J. L. Castner, Eds.). Boca Raton, FL CRC Press, 263-285. 

Decomposition is a complex process whereby the soft tissues disintegrate until skeletonization is achieved. The chemical process has been discussed extensively in previous chapters and will not be referred to here. The relationship of taphonomy to decomposition and the determination of postmortem interval is best summarized using the model proposed by Micozzi (1991) (Table 9.1). 

The presence of soft-tissue or skeletal remains in a burial environment allows for an estimation of postmortem interval using a number of techniques employed in various forensic disciplines. By the time of deposition, the methodologies of forensic pathology are generally redundant however,... 

Table 9.1 Relation of Taphonomy to Traditional Determinations of Postmortem Interval...

Additional studies involving pig carcasses has since confirmed that buried carrion demonstrate a distinct difference in the pattern of insect succession compared with what occurs on surface carrion (Turner and Wiltshire 1999). One such study established a database of insect succession and demonstrated the potential of certain species to act as determinants of postmortem interval for buried carcasses (VanLaerhoven and Anderson 1999). Dipteran species, with the exception of the family Calliphoridae, were identified as the most useful indicator species allowing for an estimation of the minimum PMI in a shallow burial environment. This assumption is based on the hypotheses that once insects are able to locate buried remains, they will colonize, feed, and develop in a normal, predictable sequence. 

More recently, the effect of postmortem interval, excavation methods, and root morphology on the rate of postmortem tooth loss has been investigated from both an archaeological and forensic context (Duric et al. 2004). In both contexts, postmortem tooth loss was shown to be a result of soft-tissue decomposition and therefore directly influenced by the postmortem interval. Additionally, the differences in root morphology were determined to be a significant factor related to postmortem tooth loss. However, an expected correlation between postmortem tooth loss and the excavation methods of the burial environment was not identified. Both of these studies represent preliminary research, and further controlled research is required to establish the value of postmortem tooth loss as a PMI indicator. 

The aim of this chapter was to review the techniques and methods currently available to forensic investigators that can potentially estimate postmortem interval or postburial interval. The estimation of time of death or deposition is one of the most important factors that forensic experts are regularly asked to determine. Although numerous methods are available in the early postmortem period (i.e., forensic pathology), once the remains become decomposed the determination of PMI becomes much more difficult to estimate. Furthermore, the methods used to estimate the PMI of exposed remains cannot always be applied to buried remains. As a result, substantial research has been conducted in recent years in an attempt to identify an accurate method for estimating PMI or PBI of remains discovered in burial environments. 

Introna, F. Jr., Di Vella, G., and Campobasso, C. P. (1999). Determination of postmortem interval from old skeletal remains by image analysis of luminal test results. J. Forensic Sci. 44, 535-538. 

Swift, B. (1998). Dating skeletal remains Investigating the viability of measuring the equilibrium between 210-Po and 210-Pb as a means of estimating the postmortem interval. Forensic Sci. Int. 98,119-126. 

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