Solvent-free strategies for developing latent fingermarks on paper: a review

With growing environmental concern and supply chain uncertainty, now is a fitting time to re-evaluate solvent-free methodologies in forensic chemistry processes. Here, this paper reviews solvent-free approaches for fingermark visualisation, including chemical fuming and vapour phase treatments, dry-transfer treatments, application of heat, and thermal paper specific treatments. After providing historical context, three objectives have been emphasised: identify feasible scenarios for implementing solvent-free methods; showcase the effectiveness of solvent-free methods relative to their nearest solution-based equivalent; and estimate the technological readiness level of each method discussed. Having reviewed the literature, dry-transfer methods of developing latent fingermarks on paper were found to be the most promising and feasible solvent-free approaches for near-term implementation. Such methods make use of standard materials and equipment commonly found in forensic laboratories, are effective at fingermark visualisation, and mitigate most of the pressing issues pertaining to environmental concern and solvent scarcity.