Exploring the applicability of equine blood to bloodstain pattern analysis

Abstract

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℃.