Crime scene investigation III: Exploring the effects of drugs of abuse and neurotransmitters on Bloodstain Pattern Analysis

Abstract

The possible misinterpretation of Bloodstain Pattern Analysis (BPA) is explored with regards to the variability in blood viscosity and surface tension values that may result from the presence of a variety of chemical additives, such as cocaine and its prominent metabolite benzoylecgonine hydrate in addition to frequently encountered neurotransmitters, namely dopamine, serotonin and epinephrine. Defibrinated horse blood was spiked with the chemicals of interest over appropriate concentration ranges and subsequent viscosity and surface tension measurements were both conducted utilising a capillary tube viscometer and a tensiometer. In the case of cocaine and its metabolite, concentrations of which encompassed therapeutic to potentially fatal levels, 10 À6 to 10 À4 M respectively, were employed and found to result in an alteration in the dynamic viscosity of defibrinated horse blood of between 1.1 to 7.8% (AE0.72 and AE0.77, N ¼ 3) and 6.4 to 9.5% (AE0.78 and AE1.52, N ¼ 3) respectively. Furthermore with the addition of variable concentrations of cocaine or its metabolite the surface tension of defibrinated horse blood was found to deviate from that of its unadulterated value of 51.0 mN m À1 (AE0.92, N ¼ 3) where for the highest concentration explored a decreased value of either 43.8 or 44.2 mN m À1 (AE0.47 and AE0.77, N ¼ 3) was measured respectively. Interestingly, in the case of the neurotransmitters, spiked into defibrinated horse blood over the range of 10 À6 to 10 À3 M, we find there to be no change or significant deviation in the respective viscosity values measured with regards to that of the unmodified blood. A possible explanation for this differing behaviour is given and where alterations in the viscosity and surface tension values of blood are noted we incorporate such variables into applicable BPA equations in order to ascertain the implications that this may induce within the Forensic interpretation of bloodstains. Consequently, through probing these equations and the employment of bloodstain spatter experiments (commonly employed within BPA) it is found that the addition of drugs of abuse and the presence of common neurotransmitters have no significant implications towards the misinterpretation of BPA.

Blood pattern analysis—a review and new findings

“…Factors like size, age, and health of the individual should also be given consideration while studying the blood stain formation. Moreover, surface tension also plays an important role in the formation of bloodstains (Larkin et al 2012). Surface tension is also varied if there is some chemical or other chemical present in the blood (Raymond et al 1996).…”

“…Viscosity in terms of blood may be described as the pressure of the flow of blood, due to shear stress or extensional stress inside the body (Bevel and Gardner 2012). An elastic-like property of a fluid due to cohesive forces between liquid molecules is surface tension (Larkin et al 2012). Blood possesses fluid nature inside the body or when it exits from the body due to an impact/injury (James et al 2005).…”

Nanomaterials-Based Electrochemical Sensors for In Vitro and In Vivo Analyses of Neurotransmitters

“…Dopamine (DA) is a neurotransmitter of the phenethylamine family that participates in metabolism, attention span, central nerve function, emotions, and neuronal elasticity. It also regulates plasma glucose levels, endocrine function, and neuroimmune regulation [40][41][42]. The DA receptor in the peripheral nervous system activates DA, and the activated DA is involved in cross-talk between the immune and neural systems.…”

Fluid dynamics topics in bloodstain pattern analysis: Comparative review and research opportunities

“…Surface tension plays a key role in the generation of drops and their impact on surfaces. Surface tension decreases with increasing temperature and is affected by chemicals present within the blood [7].…”