Experimental Study on Age Estimation of Bloodstains Based on Biological and Toxicological Analysis

The determination of the age of bloodstains in forensic investigations helps in estimating the time elapsed between incidents (such as accidents or violent crimes wherein the blood was shed) and sampling. In this study, bloodstains containing either ethanol or amphetamine sulfate and methamphetamine hydrochloride were prepared and incubated at 25°C and 50% humidity to determine their age, based on temporal changes in the relative levels of microRNA 16 (miR-16) and miR-451 after incubation. The miR-16 and miR-451 levels decreased significantly 5-28 days after incubation in the chamber. The concentration of ethanol in the bloodstains decreased rapidly during storage and became undetectable after 180 min. The concentrations of amphetamine sulfate and methamphetamine hydrochloride in the bloodstains remained almost constant throughout the experimental period. These findings indicate that the age of bloodstains can be calculated simply on the basis of the relative levels of miRNAs. Although it is difficult to utilize the concentrations of ethanol, methamphetamine, and amphetamine sulfate for estimating the age of the bloodstain, these data could provide evidence of the victim or assailant having used these substances at the scene of an accident or crime.