Latent fingermark interaction with Iron Oxide Wet Powder Suspension; an investigation into inter and intra participant variation.

Wet powder suspensions (WPS) are used to develop latent fingermarks found on a range of semi-porous and non-porous surfaces, including wetted surfaces. Despite their effectiveness the interaction between the latent fingermark and the WPS is unknown. This study aimed to investigate inter and intra person variation when latent fingermarks are developed with iron oxide WPS. Participants deposited natural, groomed eccrine and groomed sebaceous fingermarks. The latent fingermarks were developed using iron-oxide based WPS, graded and statistically analysed. A multiple regression test was used to analyse the effect of time since deposition, depletion number and condition of sweat on the fingermark grade (dependent variable). The resulting R value of 0.257 confirmed that the independent variables only had a small effect on the dependent variable. A Kruskal Wallis test indicated that there were statistically significant differences in fingermark grade between some participants (p ≤ 0.001). This suggested that some participants’ residue contained one or more specific constituents or properties that the WPS was preferentially adhering to, in a higher quantity or arrangement than other participants.