Reconsideration of bone postmortem interval estimation by UV-induced autofluorescence

Assessing the UV-fluorescence of a freshly cut cross section of the compact parts of a bone is often recommended as a first step to estimate the postmortem interval (PMI) of skeletal remains. Opinions differ concerning the cause of fluorescence and on how to categorize fluorescent properties as well as the significance of fluorescent characteristics in correlation with the PMI. In this study we evaluated the UV-fluorescence of over 200 bones with known PMI to reassess the diagnostic value of this method for differentiating between historical and recent skeletal remains. It could be shown that there is a correlation between the PMI and fluorescence colour, but not with fluorescence intensity. Furthermore, the quality of two UV-fluorescence test possibilities based on fluorescence colour was assessed by calculating the individual test efficiency, sensitivity and specificity. The results showed that blue bone fluorescence, as well as blue fluorescence combined with other colours (mainly yellow) does not allow the observer to draw any conclusions about sample age. Only overall yellow fluorescence may indicate a historical specimen. But still, 2% of all forensically relevant samples were falsely excluded, making bone fluorescent properties inappropriate as the sole criterion for deciding whether a specimen is included or excluded for further forensic investigation.