The assessment of Solstice® PF as a carrier solvent for amino acid sensitive fingermark development techniques

Amino acid sensitive fingermark detection techniques like 1,8-diazafluoren-9-one (DFO), 1,2-indanedione/zinc chloride (IND-Zn), and ninhydrin (NIN) commonly contain 1-methoxynonafluorobutane (HFE7100) as a carrier solvent for the visualization of latent fingermarks. As a result of the cessation of manufacturing by the end of 2025, and potential environmental regulations, an alternative carrier solvent must be validated to replace HFE7100. In this study, the relative performance of Solstice® Performance Fluid (PF) (trans-1-chloro-3,3,3-trifluoropropene) was compared to that of HFE7100 using 6000 natural fingermarks, aged for either one week or eight weeks, from five donors on five substrates (white copy paper, brown kraft paper, bubble envelope, lined notebook, magazine). Split fingermarks were treated with DFO or IND-Zn followed by NIN (DFO/NIN and IND-Zn/NIN, respectively) or NIN alone. All fingermarks were evaluated using a modified University of Canberra comparative scale by three assessors and, for differences in identification rates, by a former forensic identification practitioner. Results from this study showed comparable fingermark enhancement between the two carrier solvents after each treatment within the three technique sequences. There are some limitations with Solstice® PF, notably, an increase in ink diffusion and the need to store working solutions in a refrigerator or freezer.