The evaluation and validation of Phadebas paper as a presumptive screening tool for saliva on forensic exhibits.

The Phadebas Forensic Press Test is routinely used for the detection of saliva. However, assessment of the use of Phadebas paper for this purpose has not been studied extensively. The suitability of Phadebas paper as a presumptive screening tool for saliva on forensic exhibits, was investigated by analysing the following: (1) sensitivity, (2) specificity, (3) effects of temperature on sensitivity and specificity, (4) detection of saliva in mixed body fluid samples, and (5) influence of substrate porosity. The results of this study demonstrated that Phadebas paper is more sensitive to α-amylase activity and less specific for saliva than previously reported. The use of an examination temperature of 37°C had no effect on sensitivity, but increased the incidence of cross-reactivity with other forensically relevant body fluid stains. Blood, urine and vaginal secretions can inhibit the detection of α-amylase activity with Phadebas paper in mixed stains of saliva and body fluid. Substrate porosity is a weak predictor for the time taken for a saliva stain to achieve a strong positive result on Phadebas paper. Overall, this study demonstrated that the Phadebas Forensic Press Test has limitations as a presumptive test for the accurate identification of saliva.