U.S. flag

An official website of the United States government, Department of Justice.

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

NCJ Number
Date Published
February 2017
6 pages
Since bloodstain pattern analysis (BPA) provides significant evidentiary value in crime scene interpretation and reconstruction, the research described in this article developed a quantitative methodology that uses digital image analysis techniques to differentiate impact bloodstain patterns, using digital image analysis techniques to differentiate impact bloodstain patterns.
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 stains—their density as a function of position in the pattern—significantly 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)
Date Published: February 1, 2017