The development of latent fingermarks on painted walls

This research aimed to determine which fingermark processes are most efficient at developing latent marks on internal walls that have been painted. At present there is a deficiency in the quality and quantity of fingermarks being recovered from such substrates by practitioners working in the field. This issue is amplified by a lack of published research in this area. Therefore, this in-depth study sought to address some of the key challenges faced by practitioners and fill the void of knowledge in this specific area. Various methodologies were employed to undertake this research, beginning with a survey of practitioners to gauge the current practices in use across the UK. This assisted in determining the most commonly used processes to develop latent fingermarks on painted walls and the types of scenes in which painted walls are likely to be investigated. The detail gained from the questionnaire then informed the design of the experimental work carried out within this research. The experimental work consisted of numerous smaller studies to tackle specific research questions, exploring variations of paint types and brands to ascertain if these have an effect on deposited fingermarks from different donors, and establishing the primary differences between paint types and categorising these into coherent groups. The results from these studies then assisted in constructing the final set of methodologies investigating which processes are most effective at developing fingermarks on different paint types. The results from this research highlighted that practitioners do not always consider the texture or composition of a painted wall before attempting to develop latent fingermarks. In addition to this, practitioners do not generally follow the published guidelines from the Home Office Centre for Applied Science and Technology (now DSTL). The findings from the experimental work revealed that there is a distinct difference between matt paints and other non-matt paints (such as silk and bathroom paint) and therefore they should be processed differently by practitioners. The most effective treatment for matt painted walls is cyanoacrylate vapour (dyed with basic yellow 40), whereas the most efficient process for non-matt painted walls is black magnetic granular powder. This research culminated in a proposed set of guidelines designed for fingermark practitioners to assist them in creating fingermark recovery strategies. The guidelines have been constructed upon rigorous scientific evidence and should significantly increase the quality and quantity of latent fingermarks being developed ‘in situ’ on painted walls.