Sharp bone trauma diagnosis: a validation study using epifluorescence microscopy.

Identifying tool mark and involved weapon in sharp force trauma is essential to understanding the circumstances of death. But accuracy and reliability of such expert testimony remains unknown, and validation studies are rare in forensic literature. That is why, we conducted an experiment in order to determine error rates and predictive values on identifying the right implement through different types of knife-inflicted trauma. Human bone cut marks were analysed through epifluorescence microscopy. The samples were examined through a randomised, blinded, controlled study by three researchers with varying degrees of experience with direct and indirect observation of cut marks (photography). Our results showed that identifying the weapon involved is possible thanks to numerous criteria analysis. Correct classification rates were high and misclassifications rare. Asymmetric blades obtained better results than symmetric blades. Predictive values were also calculated, and the negative one reached very high levels, near 100% with regard to all the implements. Positive predictive values were more variable. But even if individual diagnoses remain in doubt, triage can be done and tools not implicated in injury can be eliminated with certainty. Moreover, our work clearly highlighted the importance of experience in such activities. A high level of experience is fundamental to obtain the best values, especially in such a context where evidence reliability is extremely important for forensic admissibility testimony in the court.