Assessment of Less Lethal Impact Munitions Using the Facial and Ocular CountermeasUre for Safety (FOCUS) Headform

Abstract

Recent social protests and gatherings in the USA have prompted law enforcement agencies to increase their use of less lethal impact munitions (LLIMs) for crowd control. Media reports and firsthand accounts have indicated that many of the LLIMs are impacting individuals in the head and neck regions. There is very little data available on the risk of injury (ROI) from LLIM impacts to these body regions. The Facial and Ocular CountermeasUre for Safety (FOCUS) surrogate headform was used to assess the ROI (fracture) from LLIM impacts. LLIMs were fired at the FOCUS headform to determine the ROI to the frontal and maxilla bones. Sixteen different LLIMs were assessed which included 12-gauge, 37-mm, and 40-mm caliber projectiles from five manufacturers. The LLIMs included bean bag style, rubber, and foam/sponge projectiles. Each LLIM was tested multiple times to determine the average ROI. The average peak resultant frontal bone force ranged from 2.0 to 7.6 kN which represented ROIs from ~ 30% up to 95%. The average peak resultant maxilla bone force ranged from 1.0 to 4.4 kN which represented ROIs from ~ 30% up to 99%. In general, 12-gauge LLIMs had a lower ROI than the larger caliber LLIMs and the rubber projectiles had a lower ROI than the bean bag style projectiles. Due to the relative thickness, the maxilla has a much lower fracture force than the frontal bone, and this was borne out in the ROIs from the maxilla impacts. Impacts to both bones showed a positive correlation between normalized energy and resultant force (p < 0.01). The slope of the plotted resultant force against the normalized energy for the 12-gauge munitions was significantly smaller compared to larger calibers for both impact sites, frontal (p = 0.031), and maxilla (p < 0.001).