A Blood Substitute for Blood Pattern Analysis of Low-Velocity Passive Stains – Its Implications in the Examination of Crime Scenes

Abstract

In forensic blood pattern analysis, the conventional trajectory reconstruction methods are based on trigonometric principles. Most of these approaches do not take into account the fluid properties of blood, a non-Newtonian fluid, leading to enormous uncertainties. For perpendicular impact blood stains, simple mathematical models based on fluid dynamics are used to determine the spreading factor and number of spines. We evaluate some of the mathematical models in this study with experimental data obtained as a function of impact height using a blood substitute. A blood substitute, which has comparable fluid properties as human blood, was preferred because using human blood for laboratory purpose has many ethical issues. The study shows that the spreading pattern and number of spines obtained from the low-velocity drip stains of circular shape using the blood substitute improves the prediction accuracy of the blood source’s vertical height from target surface. We also conducted a qualitative analysis of its spreading mechanism on different substrates with regard to surface roughness. The results indicate that a reconstructional analysis for the drip stains is possible using the suggested blood substitute. More research has to be done for evaluating its performance in all velocity ranges and all impact angles.