A comparative evaluation of the disulfur dinitride process for the visualisation of fingermarks on metal surfaces

Abstract

The disulfur dinitride process for fingermark visualisation was first reported a decade ago, with promising results obtained for a range of materials including metals. However, the friction sensitive nature of the material and difficulty of synthesis made routine use difficult. Many of these issues have since been addressed, making equipment and chemicals available to build an understanding of how the effectiveness of disulfur dinitride compares to other fingermark visualisation processes currently used on metal surfaces. This enables more informed advice to be given on selection of processes for treatment of metal items, an area of operational interest that encompasses weapons used in violent crime and the increasing incidence in metal theft. This paper reports a comparative study into the effectiveness of disulfur dinitride, cyanoacrylate fuming, vacuum metal deposition, gun blueing and wet powder suspensions on brass, bronze, copper and stainless steel. Experiments were conducted with the surfaces exposed to a range of environments including long term ageing, water/detergent washing, acetone washing and high temperature exposure. The results indicate that disulfur dinitride is an effective process for fingermark visualisation on metal surfaces, including those exposed to adverse environments, and may offer potential improvements over existing processes for those surfaces. Further work, including pseudo-operational trials, is recommended.

New alkaline-earth amidosulfates and their unexpected decomposition to S4N4

“…Moreover, our described synthetic approach demands far less elaborate conditions as M(NH 2 SO 3 ) 2 •xH 2 O precursors can be handled without an inert atmosphere or dry solvents. This finding will hopefully help to pave the way for the application of some of the many materials that can be synthesised from S 4 N 4 , 84 like polythiazyl (SN) x , which is of great interest for a range of electrical [85][86][87][88][89][90][91][92][93] as well as forensic 94,95,96 applications, by providing a method for the in situ generation of the explosive starting material S 4 N 4 for potential one-pot syntheses.…”

Imaging mass spectrometry of fingermarks on brass bullet casings using sample rotation

“…For example, experiments using techniques such as scanning Kelvin microscopy have successfully detected corrosion layers [5]. Previous studies have also shown that the modified physiochemical properties of the casing surface can be useful when trying to develop fingermarks using electrostatic [6] and vapour deposition techniques [7]. Both of these approaches have resulted in the commercialisation of devices by Consolite Forensics Ltd. (CERA TM ) and Foster and Freeman (Recover) respectively.…”

“…This means that there is the potential to retrieve other types of evidence after the ToF-SIMS imaging has been completed. The non-destructive nature of the technique is therefore very attractive and presents significant advantages when compared to conventional fingermark enhancement techniques such cyanoacrylate fuming [3], gun blueing [10], S2N2 vapour deposition [7] and palladium deposition techniques [11] which can all potentially result in the contamination of the bullet casing surface and prevent further analysis. SIMS based techniques have already been used successfully to recover fingermarks from fragments of hand grenades [9].…”

Vacuum metal deposition enhancement of friction ridge detail on ballistic materials

“…Whilst there is little specific research into the use of VMD on metallic surfaces (with the exception of a very recent comparative study by [28]), particularly regarding ballistic evidence, Tiwari et al [29] have proven its applicability on rough aluminium surfaces, with a reported 70 % success rate. VMD was chosen as the most suitable technique due to the large surface inhomogeneity.…”