Physical analysis of blood spatter pattern on concrete wall

Abstract

Bloodstain pattern analysis is the study and investigation of the physical characteristics of blood spatter in order to reconstruct a crime scene event especially homicide crime scene. This study aims to analyze blood stain patterns on non-porous wall by using real blood which mainly focused in the comparison of impact spatter between several parameters. The parameters involved were in term of amount of blood, velocity, position of victim, distance, porosity of surfaces and directionality. In this study is undertaken to analyze cast-off stain (linear spatter), impact spatter (non-linear spatter) and drip (non-linear spatter) which caused by both sharp weapon and blunt weapon. The bloodstain pattern was produced by hit the blood-soaked sponge with weapon and swung back and forth in overhead. Results showed that as amount of blood increased as the number of drops and total coverage area increased. Total coverage area also affected by the various distances to wall; greater separation was found when the distance was further. In comparison of velocity, higher velocity was tended to generate finer droplets and vice versa. Bloodstain on porous surface and non-porous surface had significant difference as more blood drips were found on non-porous wall surface. For the area of convergence determination, result showed that impact angle was proportional to width to length ratio of blood drops. As impact angle decreased, the stain was found more elongated in shape. Minimum number of blow on and sequence of blow on cast-off stain was determined through the blood trails. Based on this study, impact spatter in term of velocity, directionality, position of victim, distance, blood volume, and porosity of surfaces can be differentiated. Area of convergence and impact angle can also be determined by using stringing method and mathematical method respectively.