The impact of algae growth on forensic evidence: Considerations for latent fingermark visualisation strategies

The recovery of latent fingermarks from wetted items can present a challenge to forensic scientists. This study investigated the effect of submersion in a natural water environment in the United Kingdom on mark recoverability, exploring fingermark age prior to submersion and length of time submerged. In total, 5400 natural fingermarks were donated. These were deposited on three types of non-porous samples that were then aged for three different lengths of time, before half were submerged in a lake for three different durations. Fingermarks of identifiable quality were only recovered from samples submerged for 24 h. Samples that were submerged for longer became heavily contaminated with algae, which had a significant and detrimental effect on fingermark recovery. Only 0.7% of the marks deposited on submerged samples were visualised to be of identifiable quality, compared to 51% for the non-submerged samples. Superglue Fuming was slightly more effective than Powder Suspension on these sample types, although the difference was only statistically significant on the non-submerged stainless-steel samples and due to the low numbers of marks recovered; the results for the submerged samples should be treated with caution. This study highlights the requirement for further field work to understand critical factors in localised environments.