The enhancement and recovery of footwear marks contaminated in soil: a feasibility study

Little published research has been conducted on the chemical enhancement of soil contaminated footwear marks. Investigations into the application, including the advantages and limitations of processes available for the enhancement of footwear marks in soil were carried out as part of this study. This included a comparison of current enhancement solutions such as potassium thiocyanate, ammonium pyrrolidine dithiocarbamate, potassium ferrocyanide and bromophenol blue. The solutions were compared on the basis of sensitivity, sharpness of the colour reaction and their application to a range of commonly encountered substrates. The best preforming chemical enhancement technique for footwear impressions in soil was found to be potassium thiocyanate. Potassium thiocyanate was further explored to study the effects of aging the mark deposited as well as assessing the stability (shelf life) of the solution. It was found that the age of the mark appeared to have no significant effect on its ability to be chemically enhanced using potassium thiocyanate. The stability study of potassium thiocyanate revealed that whilst aged solutions still enhanced footwear marks, background staining, fading and deterioration in colour sharpness were all observed.