Jeffrey B. Bumgarner, Ph.D., Texas Christian University

William J. Lewinski, Ph.D., Minnesota State University

William Hudson, Ph.D., Minnesota State University

Sgt. Craig Sapp, Tempe Police Department



Every year, dozens of suspicious deadly force encounters involving police officers who have shot suspects pit the reputation of well-regarded and highly trained officers against physical evidence which suggests the officers acted maliciously. In particular, suspects are sometimes found to have been shot in the side or back despite the protestations from the firing officers that they had perceived frontal threats from the suspects. While officer malice is one possible (and sometimes probable) explanation for such shooting incidents, other explanations may also exist. This article reports the findings of a 4-experiment study involving 102 police officers in a major police department in the Southwestern United States. The results of the study demonstrate that many variables go into an officer’s ability to react to stimuli in a timely man- ner and that even in laboratory conditions, there is ample time for the threat picture to change before an officer can either turn on, or turn off, a decision to react by firing a weapon.



There has been considerable attention in criminal justice and criminological scholarly and professional literature on the use of force, including deadly force, by police officers. Com- monly, the literature has focused on officer misconduct and outright unlawfulness. Indeed, many criminal justice studies exist which examine the reasons behind violence committed by police officers against citizens.


In the landmark case of Graham v. Connor (1989), the U.S. Supreme Court declared that the use-of-force by police officers must be objectively reasonable under the 4th Amend- ment. For many contemporary observers and critics of the police who occupy seats in community organizations and academia, it is difficult for them to find examples of police use-of-force that meet the standard of objective reasonableness; for some, there is an apparent reflex to find the police at fault in almost any circumstance. They apply a standard of what is objectively reasonable to them (the critics) with the benefits of hindsight, unlimited contemplation, and complete information. They do so in spite of the Supreme Court’s admonition in Graham v. Connor to determine the objective reasonableness of use-of-force encounters by looking through the eyes of a reasonable police officer in the same circumstances and timeframe as existed when the use-of-force took place.


Instead, the standard often applied to law enforcement use-of-force action is to presume improperness and excessiveness unless the evidence clearly demonstrates otherwise. Conse- quently, when the physical evidence at first glance appears to contradict the account given by the “offending” police officer, there is almost never an extension of benefit of the doubt to such officers. Nor is there an assumption that a rational explanation which supports the officer’s ac- count might exist and is awaiting discovery.


The Sources of Police Violence


The various academic studies on police violence seem almost universally unaware of alternative explanations for violent acts committed by police officers. The studies tend to ap- proach the broad issue of police violence as always a matter of misconduct and usually a matter of criminality. Some suggest that the para-military structure and culture of modern police agen- cies contribute to violence perpetrated by police against elements of the citizenry (1-3). They would argue that police agencies must be flexible and adaptive to the changing conditions in the communities they serve and to changing societal norms (4).


A related claim is that police violence can be curtailed through organizational proactivity via human resource management and policy enforcement (5-7). Smith (8) on the other hand found that personnel and policy variables were poor predictors of police killings. Instead, levels of community violence and community racial composition were positively related to deadly force encounters (8, 9).


Other researchers have claimed that tendencies to use violence to bring about order are inherent in many individuals drawn to police work (10-12). Still another explanation relates generally to the training of police officers. James Fyfe (13) noted that police officers who are properly trained to diffuse potentially volatile situations exert considerably less force than offi- cers without such training.


Many criminal justice scholars are sufficiently concerned about the phenomenon of po- lice violence that they have called for added layers of review. Alpert and Smith (14) suggested that all force encounters between police and citizens should be routinely subject to supervisor review. The supervisor would be obligated to consider the input of not only the officer(s), but also the suspect(s) and any other witnesses. Further, they recommend that panels of “experts” also be regularly convened to determine the appropriateness of any police encounters involving force.


Indeed, scholarly criminal justice literature is saturated with many plausible explanations for police violence, along with many useful (and some not so useful) recommendations to curb it. These explanations and recommendations come from many directions, but virtually all rely on the basic premise that law enforcement needs to fix itself. In other words, the tone and tenor of the explanations and recommendations from academe is that police violence is an avoidable tragedy that can be significantly reduced if police organizations and individual offi- cers would get their acts together. Although it is true that sociological and organiza- tional variables, including the background and personalities of the of the officers, the biases of the officers, structural impediments to change, the presence or lacking of viable use-of-force policies, and many other factors may play a role in incidents of police violence, an alternative explanation for some questionable deadly force encounters does exist. The explanation is sim- ply this: many incidents involving the apparent misuse of force by police officers can be ex- plained by the realities of human psychological and physiological limitations. The nature of any inherent human limitation manifested in the real world is that it must be understood and accounted for because it cannot easily be overcome.


The Science of Human Reaction


The scientific study of how quickly the human mind and body can and do react to stim- uli (known as mental chronometry) goes back at least to the middle part of the 19th Century. For example, in 1865 Donders conducted experiments involving a mild electric shock to the

right or left foot of his subjects. The subjects would then press a telegraph key with their right or left hands to indicate which foot had received the shock. This experiment involved subjects who knew in advance which foot would be shocked, along with subjects who did not. Donders found a slight difference in response times between the two sets of subjects—approximately 1/15 of a second (15). Donders also conducted experiments measuring the differences in time between responses to a single stimulus (simple reaction time) and responses involving a choice among multiple stimuli (choice reaction time). Donders postulated that if you subtracted the simple reaction time from the choice reaction time, you would have a measure of the mental process of choice itself (16).


Another pioneer in mental chronometry was Merkel. Merkel’s studies on choice reac- tion time demonstrated that as the number of choices increased, reaction time increased as well (1885). This principle was advanced further by Hick (17) who found that reaction times not only increased when subjects were faced with choices, but that they increased linearly. This has come to be known in kinesiology as “Hick’s Law.” This axiom states that there is a stable rela- tionship existing between the number of stimulus-response alternatives and reaction time As the number of stimuli-response alternatives increase, reaction time also increases in a linear fashion (18).


Indeed, from the mid-19th Century until the mid-20th Century, the disciplines of psychol- ogy and physiology were dominated by studies and experiments that related to the capacity of human beings to react and perform in the face of stimuli requiring a response. Yet, despite the obvious applicability of such studies to law enforcement use-of-force encounters, relatively few within the circles of criminal justice, criminology, and public policy have bothered to consider the role of human performance capacity generally, and mental chronometry specifically, in the context of police use-of-force and deadly force incidents which are deemed questionable in hindsight.


Smith (19) conducted a study to collect baseline information on officer reaction times with duty handguns. In his study involving over 1,400 officers, he found that it took an average of 0.73 seconds for police officers to react to a visual stimulus by raising their already drawn pistols from a ready position (arms partially extended with firearm above waist level but below eye level) to a firing position and then firing one shot. Further, it took officers an average of 1.82 seconds to draw their weapons from their holster, bring it to eye level, and fire one shot. It took an average of 2.84 seconds for officers to draw and fire two rounds at a target from 7 yards away.


Tobin and Fackler (20) conducted a study which measured the reaction times of officers in firing drawn sidearms (but with finger outside of trigger guard as per the standard police practice) in response to stimuli, and compared those measurements with the time it takes for a person to turn their torsos away (90 and 180 degrees) from officers after posing a threat. They found that it takes officers twice as long to fire their weapons when their trigger finger is out- side the trigger guard (0.677 seconds) as compared to having their fingers on the trigger at the time of the stimulus (0.365 seconds). Further, they found that the average individual can turn his or her torso 90 degrees in 0.31 seconds and 180 degrees in 0.676 seconds. In other words, in the time it took an officer with a drawn firearm to fire his or her weapon at a threat, the sus- pect could already have turned 180 degrees away from the officer at the moment of discharge.


The findings by Tobin and Fackler have been replicated and affirmed in other studies (21-23). In fact, Lewinski (22) demonstrated that suspects can fire weapons at officers, turn and be well into their flight from the officers before the police can react and return fire.


A corollary to the plain implications of the time measurements is the difficulty an offi- cer (or any human being) has in “turning off” a reactionary decision made in the moment. In a shooting situation, once an officer decides to shoot at a suspect in response to some threatening stimulus, it is nearly impossible to abort that decision (21-22, 24-25). In fact in over 600 exam- ined cases of officer shooting decisions during a 7-year period, only one officer was identified who was able to keep himself from firing at a suspect who had already been deemed a threat and the decision to shoot had already been made (21).