Development of visualisation techniques for latent fingermarks on leather and suede

Leather and suede items are associated with diverse acquisitive and violent crimes, from petty theft and counterfeit clothing/bags to restraints and sheaths for weapons. As a consequence, they offer considerable potential for fingerprint evidence. However, this potential is seldom realised and leather is considered a “difficult” substrate, with no single reliably effective reagent for revealing latent fingermarks. The challenge here is that “leather” is in reality a diverse and complex suite of substrates, with species and authenticity (real vs faux) dependent structure, variable topography (from patent to embossed) and alterable surface finish (in terms of colour and hydrophobicity). We demonstrate the effects of these issues on the performance of a range of cyanoacrylate-based reagents, FPNatural1 powder and Physical Developer. We report selected effects of substrate variations spanning “leather” origin (bovine, caprine, cervine, ovine, porcine and faux) and surface finish (matte, embossed, nubuck, suede), and fingermark history spanning age (1 to 28 days) and environment of exposure (buried, heated, refrigerated and submerged). The success of PD is encouraging, given its wide operational applicability. The wider potential implications of the work include Customs & Excise and Trading Standards and, through species variations, wildlife crime investigations.