Collagen degradation as a possibility to determine the post-mortem interval (PMI) of human bones in a forensic context - A survey.

To find out the time since death (PMI) of a human individual, from which only skeletal remains are left is a difficult question to answer, since methods currently available don't bring concrete answers. Subsequent to our validation study on porcine bones, we focused on human bones analysing if collagen degradation would occur at a predictive rate so that the method may be used for PMI-estimation. We tried to reproduce a method for determining the Co/NCo (Collagen to Non-Collagen) ratio of porcine bones Boaks et al. demonstrated in 2014. Our study sample consisted of 37 human bones from a forensic PMI context and 11 archaeological samples; we prepared thin bone sections of 250 µm; after staining the sections we used spectrophotometry for a portion of the samples and stereomicroscopy and digital imaging to analyze the Co/NCo ratio. Detecting the Co/NCo ratio with spectrophotometry produced results much lower than those published by Boaks et al. (2014) on porcine bone samples and much lower than physiologically expected; a similar result we also got in our validation study on porcine bone samples. We, therefore, applied our new method of stereomicroscopy and digital imaging, which we previously tested on porcine bones. The samples of male individuals showed a significant reduction of the Co/NCo ratio correlating to the PMI. Nevertheless, we still consider analyzing the Co/NCo ration of human bone samples not sufficient for forensic issues. Therefore, greater reference data as well as more experience in practice are needed.