How taphonomic alteration affects the detection and imaging of striations in stab wounds

Abstract

Stabbing with a kitchen knife is a common method of homicide in Europe. Serrated knives may leave tool markings (striations) in tissues. Documentation of striations is necessary for their use as forensic evidence. Traditional methods (physical casting and photography) have significant limitations, and micro-computed tomography (micro-CT) has been trialled in cartilage to Bvirtually cast^wounds. Previous research has shown the proportion of striations in cartilage falls following decomposition. This project has investigated the effects of taphonomic alteration and documentation methods of striations in porcine skin. Fresh, decomposed, mummified, burnt and waterlogged stab wounds in a porcine analogue were excised and imaged using photography, stereo-optical microscopy and micro-CT. The proportion of striations in each taphonomic group was determined from the images by independent analysts. Striations were observed more frequently in serrated blade wounds, although they were also identified in non-serrated blade wounds. The proportion of wounds showing striations declined following decomposition. An inversely proportional linear correlation between advancing decomposition and proportion of striations existed. Dehydration (mummification and burning) rendered serrated and nonserrated blade wounds indistinguishable. Water composition affected the preservation of striations. Identification of striations gradually declined after decomposition in tap water, but persisted to a point when left in brackish water. All three techniques imaged striations; however, the optimum technique was stereo-optical microscopy due to practical advantages and specific limitations affecting photography and micro-CT. This study demonstrates the effects of taphonomic alteration on striations and suggests stereo-optical microscopy is the optimum method for their documentation.

Forensic applications of micro-computed tomography: a systematic review

“…Afterward, several experimental studies have demonstrated that micro-CT is useful to document the morphology (i.e., shape, walls, floor, angles) of stab wounds on cartilage and bones (i.e., without maceration) being even more accurate than macrophotography and scanning electron microscopy [30]. A proposed qualitative tool mark classification allowed the distinction between the weapon causing the injury (i.e., hatchet, knife) as well as the estimation of the trajectory used at tool impact [31,32].…”

Interpol review of shoe and tool marks 2016-2019

“…Several articles describe exposure effects on invasive marks, such as exposure to heat [ [144] , [145] , [146] ] or taphonomic alterations [ 147 ]. Macoveciuc et al.…”

“…Stanley et al. [ 147 ] describe the effect of taphonomic alterations on striations in skin (porcine). They see a big effect and recommend to document skin striations as soon as possible by stereo-optical microscopy.…”

Efficacy of Embalming Mixture Containing Formalin, Methanol and Water on Early Stage of Decomposition: A Validation Study

“…The primary goals of embalming are sanitization, presentation, preservation, and restoration [2]. Accident victims, stab wounds, dissected bodies or anything that mutilates the body structure have been reported to influence decomposition process [3][4][5]. Therefore, embalming decomposing bodies resulting from stab wounds require specialist attention [6].…”