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Monday, December 18, 2017 MAGAZINE Volume 1, Issue 1

The Dynamics of Shooting Incidents


by Michael A. Knox

June 5, 2012

Real-life shooting incidents occur much differently than what is commonly portrayed on television and in movies. Shooting incidents are quick, dynamic events, often taking only a few seconds from the first shot to the last. There is a vast body of research on the use of deadly force involving shootings by police. The dynamics of police-involved shootings, including an understanding of the human factors, physiology, and biomechanical aspects of police-involved shooting incidents is a standard part of law enforcement firearms training, and knowledge of these topics is common among law enforcement firearms trainers and experts.

Fear: Fight, Flight or Freeze

Artwohl and Christensen (1997) provide a working definition of fear: "Fear is an automatic physical reaction to a perceived threat that will result in predictable physical, emotional, perceptual, and cognitive changes because of high physical arousal states" (p. 33). Fear is the body's way of telling someone that his or her life is in danger and immediate action is required; "profound chemical changes" occur to make one "instinctively, and without hesitation, do one of three things to save [one's] life: fight, flight, or freeze" (p. 35). Bunting (1993) describes the nature of those changes: "As the blood flow is enhanced to the large muscles, it is diverted away from other areas of the body. The brain receives less blood; the organism is seeking only to survive and therefore has a reduced need and ability to think or reason" (p. 60). Silberman (1978) explains the concept of fight or flight:

From a physiological standpoint, what we call fear is a series of complex changes in the endocrine system that alerts us to danger and makes it possible for us to respond effectively, whether we choose to attack or flee. The first stage--the one we associate most closely with fear or tension--prepares the entire body for fight or flight: the heart rate and systolic blood pressure go up; blood flow through the brain and the skeletal muscles increases by as much as 100 percent; digestion is impaired; and so on. (p. 8)

In a shooting situation, people revert to what they have been trained to do. Adams, McTernan, and Remsberg (1980) describe this phenomon: "[W]hen you are under sudden stress and fear, your pupils dilating, your heart thumping, your lungs heaving, your adrenalin surging, your stomach and bowels in turmoil, your ability to distinguish time, colors and distance diminished, you revert without thinking to the habits your have learned in training" (p. 29). Actions become automatic, and the shooter may act without conscious thought. Without proper training, however, physical skills will probably not occur correctly under stress. Bunting explains that a "physical skill must be performed 3,000 to 5,000 times before it can occur without conscious thought in a crisis" (p. 62).

Perceptual Distortion

Artwohl and Christensen describe a number of perceptual changes that can occur as a result of fear: (1) tunnel vision may occur resulting in a loss of peripheral vision and depth perception, as well as inhibiting one's ability to see beyond a threat; (2) heightened visual clarity may--despite tunnel vision--cause one to see certain details in vivid, almost surrealistic detail; (3) time may seem distorted resulting in events seeming to have taken much longer, or to have occurred much more rapidly, than they actually did; (4) dissociation may occur in which a person feels strangely separated from the event as if it is a dream; and, (5) temporary paralysis may cause one to be momentarily unable to move despite desperately trying to do so (pp. 39-42; also Klinger, 2002, pp. 20-22).

In a survey of 72 police officers who had been involved in a shooting, Artwohl and Christensen found the following (pp. 49-50; see also Klinger, 2002, pp. 27-32; Grossman & Christensen, 2008, p. 55):

  1. Diminished Sound: 88% did not hear sounds such as gunfire, shouting, or sirens, or the sounds had "an unusual distant, muffled quality."
  2. Tunnel Vision: 82% reported that their "vision became intensely focused on the perceived threat" and they lost their peripheral vision.
  3. Automatic Pilot: 78% reported responding "automatically to the perceived threat, giving little or no conscious thought" to their actions.
  4. Heightened Visual Clarity: 65% reported being able to "see some details or actions with unusually vivid clarity or detail."
  5. Slow Motion Time: 63% reported that "events seemed to be taking place in slow motion and seemed to take longer to happen than they really did."
  6. Memory Loss for Parts of the Event: 61% reported that, after the event, there were parts of it that they could not remember.
  7. Memory Loss for Actions: 60% reported that, after the event, they could not remember some of their own actions.

Grossman and Christensen (2008) explain that these sensory distortions rarely occur in normal life; aside from deadly force encounters, such distortions occur frequently only among hunters who often experience auditory exclusion and slow-motion time (p. 121). Perceptual distortions are not limited to actual shooting situations, but may also be experienced prior to shooting, even when the shooting never actually takes place (Klinger, p. 34-41; Grossman & Christensen, pp. 115-116). Many police officers, even those who have never fired a shot on the street, have experienced perceptual distortions when faced with threatening situations that were eventually diffused without shooting. Bunting explains that "the increased auditory and visual focus and acuities are directed toward the threat" (p. 62). As a consequence, the shooter may clearly see the person he is shooting at but may not see his surroundings, and those surroundings are what provide a visual context for understanding what is happening, such as when a person falls to the ground.

Another common phenomenon is the incorrect recollection of the number of shots fired. Klinger found that in 90 cases studied, police officers could not accurately recall the number of shots fired in 37 shootings (33%); the more shots fired, the more likely the officer would not recall the number of shots fired correctly, and officers were much more likely to underestimate the number of shots fired than to overestimate that number (pp. 43-46; see also Grossman & Christensen, p. 103).

Grossman explains that, in addition to the various perceptual distortions commonly experienced by those involved in deadly force encounters, fear and panic can lead to what he terms the "endless do-loop" (pp. 101-103). In such a state, a fear-stressed person may fall into a loop in which an act is endlessly repeated despite its futility. This type of stress response leads to seemingly unimaginable behavior; people trapped in a burning building, for example, may repeatedly try to exit through a locked door rather than going to another exit. A shooter may also fire repeatedly and even continue to try to fire an empty weapon; this phenomenon can be associated with the shooter's perceptually-distorted belief that the firearm is not working because he does not hear his shots.

Wound Dynamics and Incapacitation

Contrary to television and movie depictions of gunshots, bullets rarely incapacitate instantly. Patrick (1989) explains: "Unless the tissue destroyed is located within the critical areas of the central nervous system, it is physiologically insufficient to force incapacitation upon the unwilling target. It may certainly prove to be lethal, but a body count is no evidence of incapacitation" (p. 14). DiMaio (1999) writes that incapacitation "depends not only on the characteristics of a cartridge, but also on the organ(s) injured, the severity of the wound(s) and the physiologic makeup of the person who is shot" (p. 379).

Law enforcement handgun ammunition is capable of producing lethal injuries, but its ability to inflict incapacitating injuries is much less efficient. "Physiologically, no caliber or bullet is certain to incapacitate any individual," writes Patrick, "unless the brain is hit" (p. 16). Often lethality of these wounds is a result of tissue damage due to tumbling of the bullet inside the body (DiMaio, pp. 379-380). DiMaio explains that a bullet will stop a person "dead in his tracks" when "the bullet injures a vital area of the brain, the brain stem, or the cervical spinal cord. . . . Aside from areas in the central nervous system, while a bullet may produce rapid incapacitation, there is no guarantee that it will produce instant incapacitation" (p. 381). The lethality of most gunshot wounds is due to blood loss, which is unlikely to result in immediate incapacitation because the brain can continue to function without oxygen for a short period of time; the amount of oxygen deprivation is dependent on the amount of blood flow to the brain, which, unless all blood flow to the brain is shut off, may not drop to incapacitating levels until the wounded person has lost a considerable amount of blood (pp. 254-256, 381-382). "The fact that an individual can be mortally wounded, yet still capable of aggressive actions and a threat, sometimes for a prolonged amount of time," writes DiMaio, "is not appreciated by the public whose concepts of shootings [are] derived from television and the movies" (p. 382).

Lighting, Visibility, Perception, and Reaction

The thorough and proper reconstruction of a shooting requires an understanding of issues related to how a shooter sees and perceives the intended target and the surrounding environment. While lighting conditions play an important role in vision and perception, human beings see not by quantity of light but by contrast between the target and the background. While contrast is effected by the quantity of light, even in bright conditions, low contrast between a foreground object and its background can occur. Green (2009b) explains that the "location of light is often more important than the amount of light." Contrast comes in the form of either positive contrast (light target on a dark background) or negative contrast (dark target on a light background). Differences in contrast effect the detail a shooter can see and, hence, the shooter's ability to recognize an object or the movements of a potential target individual. In order to correctly decide on a particular response, the shooter must correctly perceive and recognize what is taking place before his eyes. Green explains that lighting "affects perception of outline shape and detail differently" and that "[p]erception of general shape is faster" than perception of detail. Vision is also impaired by motion; movement "degrades fine details, the very information needed to distinguish a gun from a wallet" (Green, 2009b).

Cognitive load also plays an important role in how a shooter will perceive a threat and respond to it. During the events leading up to a shooting, the shooter must process a variety of data, some of which will contain important signal (i.e., the information needed to correctly recognize the threat and respond properly) while much of it will be noise. Responding to a perceived threat requires cognitive processing that varies according to the type of decision that must be made. Donders (1868) provided three categories for human reaction: simple, choice, and recognition. Simple reaction involves only one stimulus and one response; during research in the context of shooting events, this is typically a command to fire upon some signal such as a light being switched on or a buzzer sounding. Simple reaction is the quickest, but it rarely occurs in real-world shooting events. When it does, it will often appear in the form of a stand-off between police and an armed suspect; police wait until the suspect makes a threatening gesture such as pointing a firearm before firing. The response is known, and only the single signal is awaited. In choice response, the shooter must process multiple signals, each of which may require a different response. An officer may, for example, have to decide whether to fire his pistol, use his Taser, spray the suspect with chemical munitions, or engage the suspect in hand-to-hand combat based on the person's actions and other environmental considerations that the officer may face. In recognition response, a shooter must process multiple signals but with only one response; this is the typical shoot/don't shoot scenario in which the signals may be many, but the only decision required is whether or not to fire at the suspect (Green, 2009a).

Perception-reaction time in a shooting incident includes a number of steps:

  • acquire a visual signal;
  • process the image;
  • recognize the threat;
  • decide what action to take;
  • implement the action;
  • mechanical lag time; and,
  • time of bullet flight to the target.

All of these factors take time, and the total perception-reaction time of the shooter is dependent on the time it takes for all of these factors to play through. Hence, the firing of a shot cannot be done in response to what is perceived that instant but, instead, is done in response to what was perceived moments earlier.

It is often assumed that gunshot entry wounds that are inflicted somewhere other than the anterior portion of a person's body cannot have been the result of a shooter reacting to a bona fide threat. Law enforcement agencies around the country find themselves under fire in cases in which officers inflict gunshot wounds to a person's posterior or flank because such shootings are perceived as unjustifiable and are sometimes even labeled by critics as executions. However, the complexity of what occurs dynamically in a shooting belies the simplistic common perception; all factors in the shooting must be considered to gain a complete understanding of what took place.

Studies conducted with police officer subjects have shown that a simple, unsighted reaction time of a shooter with his finger on the trigger to a single, preplanned stimulus is, on average, 0.35 seconds; to draw and fire from a holster can take up to 2.00 seconds (Lewinski, 2002, pp. 19-23). Conversely, research has shown that a subject can turn 90 degrees in an average of 0.32 seconds with at least one test subject turning that angle in only 0.18 seconds; a 180-degree turn can be accomplished in an average of 0.58 seconds with the fastest subject making that turn in 0.33 seconds (Lewinski, 2000, pp. 20-28). In other words, during the time it takes the average police officer subject to react to the stimulus and pull the trigger, the target person can turn completely around and be facing away from the shooter. A graphic by the Force Science Research Institute illustrates this concept. It is also important to recognize that a person need not be facing an intended target such as a police officer or armed civilian to pose a deadly threat; a firearm can be pointed over one's shoulder or around one's torso and still be fired accurately. In such a case, shots fired at the threatening person will likely strike him in the flank or even in the back.

Research has been conducted to determine how long it takes a person to stop pulling the trigger. Bumgarner et al. (2006) found that, when firing repeatedly and responding to the simple stimulus of a light being switched off, it takes the average police officer subject 0.35 seconds to stop pulling the trigger (pp. 18-23). Jason (2010) found that of 36 tests in which officers were instructed to fire multiple, rapid shots, until a simple "cease fire" stimulus was given, 44% of the time the shooter fired one extra shot, 17% of the time the shooter fired two extra shots, and 8% of the time the shooter fired three extra shots (pp. 11-14). Indeed, shooting incidents are fast-paced events.

Witness & Officer Statements

The testimony of witnesses is critical to a successful and proper crime scene reconstruction. Witnesses are often able to provide key contextual information that allows the crime scene analyst to piece together physical evidence in a meaningful way and to make appropriate connections between items of physical evidence that might not by themselves provide a complete picture of what took place. When employing information elicited from witness testimony, it is important to consider both the credibility and reliability of the witness. A credible witness is one who is apparently trustworthy and free from unmitigated bias; a reliable witness is one whose testimony comports with the physical evidence.

Moran (2007) describes the necessity of evaluating witness statements against the physical evidence. "Statements made by victims, suspects, and witnesses . . . can provide information as the basis for the development and testing of scenarios and theories," writes Moran. "[O]bservations by these participants can direct significance to certain items of physical evidence that might not otherwise be apparent to investigators . . . ." Moran writes that witness statements "should not be relied on as fact" and explains that "physical evidence and observations made at the shooting scene should be consciously correlated with participant statements to either support or refute them" (p. 305).

Even interviews of trained police officers involved in shooting incidents must be evaluated critically. Artwohl and Christensen explain that "human memory is fallible" and that fact is "one of the most important things to remember about investigating a shooting . . . ." "Few people have a photographic memory that is a totally accurate representation of reality," they write. "Human memory is subject to distortions and omissions even under nonstressful circumstances, and the stress of a traumatic incident only makes it worse" (p. 245). Inaccurate statements are not necessarily deceptive ones. Participants in a shooting incident will recount what they recall, but their recollection may be distorted. Fast-paced events such as shooting incidents leave great room for witnesses to confuse time-lines and event sequencing.

Grossman (1995) likens the information obtained from participants in a critical incident to blind men feeling an elephant. "Like the blind men of the proverb," Grossman explains, "each individual feels a piece of the elephant, and the enormity of what he has found is overwhelming enough to convince each blindly groping observer that he had found the essence of the beast" (p. 95). Grossman explains that it is important to put the testimony of each witness into context to gain insight into the complete picture. Grossman and Christensen (2008) explain that one of the blind men "says that he felt a tree, another reports a wall, and the third says he felt a big snake. In the end, each person comes away with different impressions of the experience, and only by gathering them all together can we hope to get a complete impression" (pp. 114-115).


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Lewinski, W. J. (2002). Biomechanics of lethal force encounters--officer movements. Police Marksman, 27(6), 19-23.

Moran, B. R. (2007). Shooting incident reconstruction. In W. J. Chisum & B. E. Turvey (Eds.) Crime reconstruction (pp. 215-312). Burlington, MA: Academic Press.

Michael Knox is a forensic consultant and is the owner of Knox & Associates, LLC , a Jacksonville, Florida-based forensic consulting company that specializes in firearms, ballistics, and crime scene reconstruction. He was a police-officer/detective with the Jacksonville Sheriff’s Office for over 15 years having worked in patrol, DUI enforcement, crime scene investigations, and traffic homicide investigations. He was the training coordinator for the agency’s crime scene unit for several years and has provided crime scene training in Peru, the United Arab Emirates, the Republic of Georgia, and around the United States. He has testified as an expert witness in crime scene reconstruction in state and federal courts in Florida, Alabama, Texas, and Illinois. He holds a Bachelor of Science degree in mechanical engineering from the University of North Florida and Master of Science degree in forensic science from the University of Florida. He also holds current certification as a crime scene reconstructionist through the International Association for Identification and accreditation as a traffic accident reconstructionist through the Accreditation Commission for Traffic Accident Reconstruction.