The effectiveness of the RSID confirmatory test kit for human alpha amylase: the effects of environmental factors and substrate materials

Abstract

The investment in time and money that DNA analyses involves, provides a justification for forensic laboratories to carry out prior tests to ensure the presence of biological fluid in samples. The RSID kit has already been evaluated for forensic use, but its effectiveness on forensic casework samples is almost impossible to predict. Moreover, forensic reports presented before a court of law must justify the methods used to generate their findings. Consequently, trials to know how factors – such as the characteristics of the donor, the substrate and environmental conditions – can affect the kit’s efficacy are essential. This study evaluates some of these factors. For this aim, samples were made using lyophilized human salivary alpha amylase, with known concentrations, on different materials. Then were distributed in two groups, A (not protected) and B (stored and protected) to evaluate possible differences in the effectiveness of the test. The results show how those factors affect the kit’s performance, and, moreover, demonstrate that, contrary to the results that the literature provides for samples in solutions, the kit is more effective on saliva than on alpha amylase. Once again, this highlights the different behaviour of forensic casework samples compared with those that were used in the kit’s evaluation.