More about RSID-saliva: the effect of sample age and the environment on the test’s efficacy

Abstract

In addition to the genetic profile of the donor, body fluid stains can provide forensic scientists with a lot of other information. Knowing the nature of these fluids can be fundamental in categorising a crime and reconstructing the events involved. To do so, it is necessary to have the means to confirm the origin of the body fluids. Prepared commercial kits to evaluate haemoglobin and prostate-specific antigen have been utilised for many years in forensic laboratories. The RSID-saliva test performs a similar function in the determination of this body fluid. The test’s sensitivity and specificity have been confirmed in previous studies, but in order to apply it to real samples it is also necessary to evaluate its efficacy on fluids exposed to real conditions of deterioration. The present study deals with mock casework samples, introducing the factors of the age of the sample and the effect of contact with the environment. The influence of the type of material is also evaluated. The results show the resistance to these factors of 40-day-old saliva samples. Consequently, in the study conditions, positives can be obtained using RSID-saliva. Thus, the data provided indicate that RSID-saliva is a useful forensic test for examining evidentiary items suspected of containing saliva.