title: Quantitative Differentiation of Bloodstain Patterns Resulting from Gunshot and Blunt Force Impacts.
abstract: Bloodstain pattern analysis (BPA) provides significant evidentiary value in crime scene interpretation and reconstruction. In this work, we develop a quantitative methodology using digital image analysis techniques to differentiate impact bloodstain patterns. The bloodstain patterns were digitally imaged and analyzed using image analysis algorithms. Our 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% smaller than the mean drop stain size in blunt instrument patterns. In contrast, we demonstrate that the spatial distribution of the droplet stains-their density as a function of position in the pattern-significantly differs between gunshot and blunt instrument patterns, with densities as much as 400% larger for gunshot impacts. Thus, quantitative metrics involving the spatial distribution of droplet stains within a bloodstain pattern can be useful for objective differentiation between blunt instrument and gunshot bloodstain patterns.
authors.affiliation: University of California, Forensic Science Graduate Program, 1909 Galileo Ct. Ste B, Davis, CA, 95628.
authors.forename: Sonya
authors.initials: S
authors.lastname: Siu
authors.affiliation: University of California, Forensic Science Graduate Program, 1909 Galileo Ct. Ste B, Davis, CA, 95628.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Pender
authors.affiliation: Sacramento County District Attorney, Laboratory of Forensic Services, 4800 Broadway, Sacramento, CA, 95820.
authors.forename: Faye
authors.initials: F
authors.lastname: Springer
authors.affiliation: University of California, Forensic Science Graduate Program, 1909 Galileo Ct. Ste B, Davis, CA, 95628.
authors.forename: Frederic
authors.initials: F
authors.lastname: Tulleners
authors.affiliation: Department of Chemical Engineering and Material Science, University of California, 1 Shields Ave, Davis, CA, 95616.
authors.forename: William
authors.initials: W
authors.lastname: Ristenpart
keywords: blood drop velocity; bloodstain pattern analysis; forensic science; image analysis; impact pattern