Saliva-Blood Adulteration May Impair Age of Stain Determination by RNA Species

Abstract

Analysing the relative quantity of the housekeeping genes β-actin and 18S rRNA has been proposed as genetic method of determining the age of bloodstains collected from crime scenes. However, the measured quantities of these housekeeping genes could be affected in cases of the contamination of bloodstains with another body fluid from the same individual or different individuals. This study investigated the effect of mixing bloodstains with another bodily fluid, namely saliva, on the values of the relative quantity ratio (RQR) between the quantities of β-actin to 18S rRNA and thus on the estimation of the age of the bloodstain. RNA was extracted from fresh and aged blood and saliva separately and in combination with several permutations. RNA was reverse transcripted and quantified for β-actin and 18S rRNA. The data revealed significant changes in the RQR value of β-actin to 18S rRNA in the blood-saliva mixture as compared to separate samples of blood and saliva.