Measurements and Comparative Considerations of Velocities of Primary Bloodstain Spatters using a High Speed Camera

Seo, Young Il; Moon, Byung Sun; Cho, Young Jin; Jeon, Woo Jeong; Kim, Seong Jin; Son, Bu Nam; Kim, Ki Jeong; Kim, Young Gyu; Choo, Chang Woo; Lee, Seung Hoon; Hong, Woo Han; Lim, Chae Won; Lee, Jong Hoon; Ryu, Kyung Jin; Yu, Je Seol; Choi, Yong Seok; Park, Nam Kyu

Abstract

Bloodstain pattern analysis is a forensic discipline that reconstruct events of a crime scene by analyzing sizes, shapes, distributions, positions of bloodstains. Bloodstain pattern can be classified into the low velocity, medium velocity, and high velocity system. Velocities in this system represent the velocity of the wounding agent (the force applied) and not to the velocity of the blood in flight. Thus there is no reference system about the velocity of the blood in flight in the existing bloodstain classification system. Applying bloodstain pattern analysis to the real crime case, we needed to have the reference system of velocities of impact spatter, cast-off spatter, and expectorate spatter. Therefore we measured the velocities of these spatters using high speed camera and we analyzed the results. In this experiments the average velocity of impact spatter that generated by swinging a hammer with all experimenter's strength at the pool of blood is about 4.7 times faster than that of swing cast-off spatter that generated by swinging a red-wat hammer with all experimenter's strength, and about 3.9 times faster than that of expectorate spatter that generated by emitting blood from the mouth with all experimenter's strength. The velocities of cast-off spatter and expectorate spatter, however, showed similar distributions. Our experiments that measure the velocities of droplets of blood spatters in flight under the specific conditions that generated at fastest speed can give some reference to the classification system of velocities of bloodstains which is not distinct up to now, as well as some real bloodshed crime cases.