Quantitative Differentiation of Bloodstain Patterns Resulting From Gunshot and Blunt Force Impacts

The bloodstain patterns were digitally imaged and analyzed using image analysis algorithms. The analysis of 72 unique bloodstain patterns, comprising more than 490,000 individual droplet stains, indicates that the mean drop size in a gunshot spatter pattern is at most 30 percent smaller than the mean drop stain size in blunt instrument patterns. In contrast, the project demonstrated that the spatial distribution of the droplet stainstheir density as a function of position in the patternsignificantly differed between gunshot and blunt instrument patterns, with densities as much as 400 percent larger for gunshot impacts. Thus, quantitative metrics that involve the spatial distribution of droplet stains within a bloodstain pattern can be useful for objective differentiation between blunt instrument and gunshot bloodstain patterns. (Publisher abstract modified)