The Impact of Scalp Hair on Gunshot Residue Deposition: A Forensic Approach to Range of Fire Determination

Range of fire determination in shooting fatalities classically depends on the gross presence, distribution, and density of visible gunshot residue (GSR), including soot, stippling, and bullet wipe surrounding the entrance wound. Scalp hair has been suggested to interfere with GSR deposition in head wounds, but few experimental studies have systematically addressed this variable. Misinterpretation of GSR findings in hair-covered wounds carries significant medicolegal consequences. In this study, controlled discharge testing was performed using a Ransom International Forensic Ballistic Machine. Three cosmetology-grade mannequin heads with synthetic vinyl skin and 100% human hair were used: short, tightly curled (max 6 inches); long, straight (max 22 inches); and medium, straight (max 12 inches). Five firearms (.22 Long Rifle, .40 S&W, 9 mm Parabellum, .45 Auto, .223 Remington) were discharged at 2 inches and 6 inches into five scalp regions (left temporal, left parietal-occipital, occipital, right parietal-occipital, right temporal), producing 50 defects. Visible GSR was assessed before and after shaving. Visible GSR was present in 19 of 25 defects (76%) at 2 inches and nine of 25 (36%) at 6 inches. Within tightly curled hair, GSR was visible in only seven of 20 defects (35%). All .22 Long Rifle defects showed visible GSR (10 of 10). Results reveal that dense, tightly curled scalp hair can substantially reduce or eliminate visible GSR even at short range. Absence of visible GSR in hair-covered defects should not, alone, be interpreted as evidence of distant or indeterminate range of fire.