Long bones after suspected “grave robbery”: a comparison of different methods for the estimation of the post mortem interval

Estimation of the postmortem interval (PMI) of found bones is an important and challenging part of forensic osteology assessments. This study examined human long bones that had been taken from cemeteries and hoarded by a "bone collector". Based on the police investigation and own investigation into the length of grave leases in the pertinent cemeteries, the narrowed down PMI for the bones was between 20 and 100 years. Our aim was to evaluate the suitability of the UV-fluorescence and luminol methods in determining the PMI of these bones and to assess the reliability of the results for forensic practice. Based on macroscopic criteria, 201 bones were classified into various PMI groups. Freshly sawn bone surfaces were then assessed with UV-fluorescence and luminol. The UV-fluorescence examination showed a weak to mediocre correlation between the intensity of UV-fluorescence and the PMI estimated by macroscopic criteria. Surprisingly, the luminol test did not reveal a negative correlation between the degree of chemiluminescence and macroscopically estimated PMI. Within a PMI span of up to 100 years, the extent of UV-fluorescence can serve only as a rough indicator of PMI. Alone, the method does not suffice to identify forensically relevant PMIs. Likewise, the luminol test does not reliably distinguish between bone finds with and without forensically relevant PMI. Nonetheless, the assumption that a negative luminol-test still speaks for a historical find appears to be justified, and, at least in combination with other tests, the luminol test can be used.