by Zack Kowalske, MS, CCSR, Delta-5 Forensic Laboratories
In the past few years, firearm mortality has averaged more than 14,000 persons annually. In light of current events, the use of deadly force by law enforcement is the subject of prevalent scrutiny. As reported by the Washington Post, 1,003 fatal law enforcement shootings occurred in 2019. This article is not an op-ed intended to debate the causality of deaths related to law enforcement function; but instead provide considerations for the crime scene reconstructionist and layperson based in science.
Shooting incidents are dynamic and occur quick. They are rooted just as deeply in neuropsychology as they are in ballistic physics, more specifically in the actions of mental chronometry. Several years ago, I was retained for a shooting reconstruction in a wrongful death litigation for a fatal officer-involved shooting. The death involved a foot chase and the officer firing during the course of the chase after claiming to have a firearm pointed at him. The majority of the incident was captured on video surveillance, which allowed me to break the incident down second by second, frame by frame. In the forensic sciences we report fact, remaining objective, and not opining in “Monday morning quarterback” exercises. So often in shooting incidents there is no video, and reconstruction experts must rely on applied principles of physics, pathology and trigonometry to establish the facts of the events that transpired. In this case, that element was removed and the analyst could focus on the more subtle science of action and reaction.
Mental chronometry is the study of reaction time, the time measured in milliseconds for cognitive processing and reaction to a stimulus. In law enforcement or deadly force encounters, that decision tree is the simple foundation in a complex event; the stimulus (firearm, taser, bat, etc.) is presented to the shooter, the shooter perceives the visual information and cognitively processes the display to be a threat. The brain then has to decide how to respond to the information. In this example, the brain recognizes the display to be dangerous to its survival and decides that deadly force is necessary. The brain then sends the neurological impulse to the muscles to draw, point, aim, and pull the trigger. It then reassesses the sensory input to repeat the decision process; and all of this happens in a time span of milliseconds or the blink of an eye.
“The various circumstances of use-of-force events, internal psychological states, and physiological aspects of the human officer all can impact RT [reaction time]. Decision making within the brain while under high stress is not the same as decision making during ordinary events,” Hough et. alwrote in 2017. There are many published studies on this topic, but allow me to refer to just a few for consideration in any shooting incident.
In Evaluation of Law Enforcement Officer Combat Handgun Skills, the reaction time to various stimuli of 1,400 police officers was examined. Smith’s study determined that, on average, it took officers 0.73 seconds to raise an already drawn firearm and fire one shot, and 1.82 seconds when drawing from a holster was added to the reaction. The reaction time when adding distance of seven yards and a second shot was 2.84 seconds.
In their study, Officer Reaction-response Times in Firing a Handgun, Tobin and Fackler add the variable of suspect positioning. They concluded that an average subject could turn their torso 90 degrees in 0.31 seconds and 180 degrees in 0.67 seconds; this study was in conjunction with officer shooting reaction times.
Research projects such as these are critical, in that they demonstrate how a subject can display a threat and then turn before the officer is able to pull the trigger, a critical fact for the crime scene reconstructionist to understand when examining a case in which the subject sustains gunshot wounds to the back or posterior aspects.
Lastly, Bumgarner et al. empirically demonstrate how changing the response “mid-flight” is near physiologically impossible. To not pull the trigger due to a rapidly changing environment after the brain has made the decision to fire adds another key factor for consideration in evaluating shooting incidents.
These findings don’t just apply to law enforcement use of force encounters, but the broad spectrum of casework forensic examiners investigate. The evaluator or investigator cannot ignore biology and empirically based science when faced with flight paths or wound tracts that are unfavorable on face value. It is critical that all aspects of an incident be objectively analyzed so facts can accurately be reported, whatever they may be.
References:
Smith, G. (1990). Evaluation of law enforcement officer combat handgun skills. Smith and Wesson Academy Newsletter, November, 7-8.
Tobin, E.J. and Fackler, M.L. (1997). Officer reaction-response times in firing a hand gun. Wound Ballistics Review: Journal of the International Wound Ballistics Association, 3(1), 6-9.
Bumgarner et al. (2007). An Examination of Police Officer Mental Chronometry: “I Sware…I Don’t Know How I Shot Him in the Back”. The Scene Journal of The Association for Crime Scene Reconstruction.