Characteristics and time-dependence of cut marks and blunt force fractures on costal cartilages: an experimental study

Purpose: The distinction between cut marks and blunt force injuries on costal cartilages is a crucial issue in the forensic field. Moreover, a correct distinction may further be complicated by decomposition, so the need arises to investigate the distinctive features of lesions on cartilage and their changes over time. Methods: This study aimed to assess the stereomicroscopic features of cut marks (performed with six different knives) and blunt fractures (performed with a hammer and by means of manual bending) on 48 fragments of human costal cartilages. Moreover, in order to simulate decomposition, the cut and fractured surfaces were checked with stereomicroscopy and through casts after 1 and 2 days, 1 week, and 1, 2 and 4 months of drying in ambient air. Results: In fresh samples, for single and unique cuts, striations were observed in between 44 and 88 % of cases when non-serrated blades were used, and between 77 and 88 % for serrated blades; in the case of “repeated” (back and forth movement) cuts, striations were detected in between 56 and 89 % of cases for non-serrated blades, and between 66 and 100 % for serrated blades. After only 1 week of decomposition the detection rates fell to percentages of between 28 and 39 % for serrated blades and between 17 and 33 % for non-serrated blades. Blunt force injuries showed non-specific characteristics, which, if properly assessed, may lead to a reliable distinction between different cut marks in fresh samples. The most evident alterations of the structure of the cartilage occurred in the first week of decomposition in ambient air. After one week of drying, the characteristics of cut marks were almost undetectable, thereby making it extremely challenging to distinguish between cut marks, blunt force fractures and taphonomic effects. Conclusion: The study represents a contribution to the correct assessment and distinction of cut marks and blunt force injuries on cartilages, providing a glimpse on the modifications such lesions may undergo with decomposition.