Alternative strategies for friction ridge detail recovery from ballistic evidence

Abstract

Fingermarks are one of the most important and frequently encountered pieces of evidence in a crime scene. Ballistic material may also be recovered from a crime scene where firearms have been involved. The current recovery rate of identifiable fingermarks on ballistic evidence is quite low. The study herein aims to improve the knowledge base in relation to the enhancement of fingermarks on ballistic surfaces by employing various fingermark enhancement techniques that have been underutilised, while also using Gas Chromatography - Mass Spectrometry and a new fingermark deposition protocol to further strengthen our understanding of mark enhancement. A quick and cost-effective Gun Blue protocol with exceptional results on unfired ballistic material that had been exposed to a variety of environmental conditions and some well enhanced fingermarks (from various donors) on cartridges fired by different firearms is studied and proposed as a routine police casework technique. Vacuum metal deposition, a technique that was mostly visited for enhancing marks on plastic surfaces, is revisited for mark enhancement on ballistic material. The results of 2 different studies with different donor pools, showcase the suitability of the technique for brass surfaces and fired brass cartridge cases with a wide range of donors (20), while also being effective on older fingermarks (2 months old). Our results show the potential of VMD to be a used in police routine casework, when the surface in question is brass. The use of Gas Chromatography - Mass Spectrometry lead to the identification and quantification of compounds that are able to withstand the extreme conditions of firing, and thus providing information on which fingermark enhancement methods would be the best candidates for fired cartridge cases. Squalene, palmitic acid and cholesterol were the compounds that were most consistently present in the fingermark samples, while also being less affected by the time elapsed after deposition. Our findings in this chapter explain the favourable results Gun Blue enhancement generated on old fingermark samples. An artificial fingermark was created as a way to generate reproducible fingermarks by loading the fake fingermark with a precise amount of compounds found in fingermarks prior to each deposition. Our preliminary results demonstrate the additional advantage of this protocol, which is the potential it has to pinpoint, which compounds facilitate fingermark enhancement for different development methods. This could result in a better understanding of all fingermark enhancement methods and therefore could lead to improved recovery rates of fingermarks.