Crime scene investigation: The effect of drug contaminated bloodstains on bloodstain pattern analysis

Abstract

We explore for the first time the relationship between the drug content of blood and its corresponding physical property, viscosity, and examine whether this effect can lead to the miss-interpretation of the Bloodstain Pattern Analysis (BPA) of drug contaminated bloodstains found at crime scenes. The viscosity of amphetamine spiked blood was measured using a capillary tube viscometer with amphetamine concentrations explored over the range 3.0 × 10⁻⁷ to 4.1 × 10⁻³ mol dm⁻³ equating to therapeutic and potentially fatal levels respectively, which are commonly found in Crime Scene Investigation and were found to result in a viscosity change; the range of 0.5–11.0% respectively. Based on these observations the estimation of variances within BPA was calculated by introducing the variability of the viscosity into previously derived equations. We find with increasing amphetamine concentrations an increase in the percentage change (corresponding to a decrease in dynamic viscosity) of blood viscosity occurred; this variation theoretically induces a 0.61 mm diameter alteration (2.9%) of resultant bloodstains. The effect of drug contaminated bloodstains on BPA is currently an under explored area within the field of forensic science which requires further investigation due to BPA's inclusion in legal proceedings.