The effect of household corrosive substances on latent fingermark development in the context of deliberate corrosive substance attacks

Corrosive substance attacks (CSA) are a prevalent issue in the UK with 525 offenses involving a corrosive substance reported to the police in the year ending March 2022. Easy availability, low cost, and concealability in public are common reasons for choosing a corrosive substance as a weapon. The Metropolitan Police revealed that 68% of 1849 CSA cases resulted in no suspect identified or evidential difficulties. There is limited research into the effect of corrosive substances on latent fingermarks. This study aimed to determine the potential for fingermarks to be recovered from surfaces exposed to a household corrosive substance within the context of a deliberate CSA. Natural and sebaceous-loaded fingermarks were exposed to Domestos bleach, Harpic limescale remover (hydrochloric acid-based) and lemon juice. Harpic limescale remover had the most detrimental effect, with only 7.1% of fingermarks (n = 378) exposed being identifiable (defined as sufficient clear ridge detail for identification) after enhancement, followed by bleach with only 10.3% of fingermarks (n = 378) identifiable. Lemon juice had the least detrimental effect on fingermarks, with 40.5% fingermarks (n = 378) identifiable compared to 53.4% for the controls (not exposed to any substance; n = 378). Throughout the study, fewer natural fingermarks were identifiable after exposure to corrosive substances compared to sebaceous fingermarks which was as expected. Overall, this study demonstrated that there is potential to recover latent fingermarks, depending on their composition, following exposure to a household corrosive substance. This area warrants further research to establish best practice to maximize the potential to recover identifiable fingermarks.

The effect of corrosive substances on fingermark recovery: A pilot study

Corrosive substance attacks have become a growing issue within the UK. Although most commonly occurring in gang-related offences, there are high profile instances where this type of attack has been used to attack women to disfigure and destroy livelihoods. Despite the increase in such attacks, there has been very little published research into the recovery of forensic evidence from items used in these crimes. The effect of corrosive substances on the recovery of different types of forensic evidence is unknown, and there is no guidance for laboratories processing exhibits contaminated with corrosive substances regarding optimum treatments. This pilot study focused on establishing the effectiveness of a range of fingermark visualisation processes in recovering fingermarks on surfaces exposed to concentrated sulfuric acid (acid) and potassium hydroxide (alkali). Results indicate that on non-porous surfaces vacuum metal deposition and powder suspensions remain effective, and on porous surfaces fingermarks could still be visualised with physical developer. Alkalis were found to be more detrimental than acid environments in this limited study. The results demonstrate that fingermark recovery is still feasible on surfaces exposed to corrosive substances and provides encouragement that treatment protocols could be developed for this type of exhibit.