Bloodstain pattern analysis (BPA) is the forensic application of the interpretation of distinct patterns which blood exhibits during a bloodletting incident, providing key evidence with its ability to map the sequence of events. Here, we explore the use of equine blood and investigate its suitability within the field of BPA. Blood is a complex fluid, and finding a suitable safe substitute to human blood that encompasses all of its characteristics has been the focus of many investigations. Animal blood has been concluded as the closest and therefore the most suitable alternate. However, it seems that currently only porcine blood is most prominently utilised.In this study, equine blood was investigated, using two different anti-clotting methods, where blood impacts were explored over a typical range of varying impact velocities upon a selection of commonly encountered surfaces. Key BPA parameters, such as the diameters of the resulting bloodstains, number of spines and area of origin were measured, which were subsequently applied into previously derived BPA equations.We find that defibrinated equine blood is a suitable alternative and offers the same conclusive outcomes to human blood. This gives bloodstain pattern investigators and researchers an additional choice of blood which can be of benefit when certain bloods are difficult to attain or when the activity involves the usage of a large quantity of blood. Additionally we explore the effect on BPA of aged blood, which revealed a significant decrease in stain diameter of up to 12.78 % when blood has been left for 57 days. A shelf life of no more than 12 days is recommended when blood is refrigerated at 4℃.

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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.

Bloodstain pattern analysis (BPA) involves the interpretation of distinct blood patterns found at crime scenes following a violent act. In this paper, we explored for the first time the effects of surface temperatures upon blood impacting a horizontal surface (steel) with its implications in BPA explored. Specific surface temperatures were explored over the range 24-250°C which relate to the four major boiling regimes of liquid media; natural convection, nucleate boiling, transition boiling, and film boiling, where a series of blood drops tests were performed at varying impact velocities. Blood was found to separate into its components at temperatures of 50°C+, displayed as temperature induced blood rings, where a single secondary and a series of further inner rings are exhibited. This consequently led to the development of a new constant Cd heated expressing the decrease in spread factor (D(s)/D(o)) at the secondary ring.

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