Forward Spatter Bloodstain Pattern Analysis: AO Estimation Using Image Processing and Numerical Modeling

Abstract

The aim of examining the forward spatter bloodstain patterns of gunshot wounds is to accurately describe the relationship between the victim, the culprit, and the crime scene. The purpose of this study is to determine the approximate location of the blood source, i.e. the victim, at the crime scene by using an image processing and numerical modeling approach. To achieve this, an experimental setup is designed with cardstocks and a cow blood-soaked sponge. In total, twenty forward spatter patterns are obtained onto cardstocks after successful shootings. In the post-processing phase, ellipses on the cardstocks are detected by processing the forward spatters in MATLAB. To achieve this, ellipse properties are identified for calculating the impact angles. The impact angles are then utilized as inputs to the tangent method within the program to estimate the Area of Origin (AO_x). For visualization, 2D and 3D images are generated. In conclusion, it is observed that the program works the best in determining the AO_x, for the scenarios where the real AO_x distances (blood source to target distances) are 35 cm, 50 cm, and 100 cm respectively. The program’s weakness while determining AO_x for the source distance of 5 cm is also reported. It is necessary to improve the program for short blood source-to-target distances and long shooting distances. It can be concluded that image quality is also a key factor for post-processing as it might mislead the results with visible ellipses.