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Research: Startle response and firearm draws

Recent findings provide empirical evidence that motor movements, like the firearm draw performance, can be initiated before the startle response is completed


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Originally published on the Force Science Institute website. Republished here with permission.

By Lewis “Von” Kliem, MCJ, JD, LLM

In 2013, Force Science published the “Traffic Stop Study,” in which researchers assessed the relative safety of driver-side and passenger-side approaches by officers. During the research, the officers’ reactions were observed in response to an unexpected, simulated firearm assault.

The primary focus of the researchers was to measure the amount of time officers from various positions alongside the car could reach the “mitigation zone.” The mitigation zone represented the area around the vehicle where an officer faced a reduced risk from a firearm assault. [1]

In addition to measuring the time of assault, the officer’s type and duration of movement, and the time it took officers to reach the mitigation zone, researchers in the Traffic Stop Study observed the officer’s “startle response.” The startle response is a largely nonconscious physical response to a sudden, intense stimulus. [2] These responses often occur within milliseconds and can involve a blink, the activation of neck muscles (e.g., neck flexion, shrugging), increased heart rate, hand grasping, fist clenching, and various defensive arm and leg movements. [3]

Researchers investigated the types of startle responses exhibited by the officers and documented the influence these responses had on tactical choices and overall movement speeds. Not surprisingly, most officers attempted to draw their handguns in response to the sudden armed assault. This occurred despite the driver’s gun already being presented, aimed, and held within a foot of the officer. The rapid and close nature of the firearm assault predictably triggered an observable startle response, after which some officers attempted to draw before retreating, some during their retreat, and others drew only after reaching the mitigation zone (see Figure 1).


Figure 1: 2013 Force Science Traffic Stop Study.

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The full study, titled, “The Influence of Officer Positioning on Movement during a Threatening Traffic Stop Scenario,” is highly recommended reading for trainers as the observations highlight the limitations of human performance when facing sudden, violent assaults.

The Next Question: Startle Response and Draw Performance

Although critical lessons were learned by analyzing the officers’ reactions and responses in the 2013 Traffic Stop Study, researchers recognized that an important question was left unanswered. How did the startle response influence firearm draw performance?

In 2022, Dr. Bill Lewinski, senior researcher at Force Science, joined Dr. Michael Kantor, Dr. Dane Bartz, and Dr. Robert Pettitt in continuing to explore this critical issue. [4] Published in the Journal of Forensic Biomechanics, their latest research, “Startle Response and Firearm Draw Performance in Law Enforcement Officers during a Lethal Force Simulated Domestic Assault,” explores the duration of the startle response, and its influence on officers’ firearm draw performance.

Startle Response and Firearm Draw Performance

In lab settings, firearm draw performance (the ability to draw and fire a single round) has been measured to average between 1.5 and 1.8 seconds (± 0.46 s). [5] These measurements represent the speed at which people were able to draw, point and fire a pistol in response to non-threatening start signals (e.g., visual, or audible signals). [6]

In the Traffic Stop Study, the complex variables that appeared to influence the draw performance included the initial startle response, communication, the movement to draw, and the movement to retreat. Although researchers were able to measure the officers’ accelerated heart rates and initial reaction to the “assault,” the complexity of the response did not allow them to record the duration of the startle response or accurately assess its influence on overall firearm draw performance.

In this latest study, researchers isolated the startle response and measured its duration with motion sensors. This allowed them to observe how the startle response might impact the overall response time (firearm draw performance) when initiated by a simulated, unexpected lethal threat (the rapid presentation and audible discharge of a firearm).

The Startle Response Study

To trigger a startle response and firearm draw performance, researchers had participant officers respond twice to the scene of a simulated past domestic disturbance. At the residence, officers were expected to interview the female spouse regarding her male spouse’s alleged physical abuse. The male spouse had departed the residence prior to police arrival. After approximately 60s into the interview, the researchers concluded the first trial and the officer was escorted from the scene.

During the second trial, the officer was given the same instructions and was again expected to interview the female spouse. After 20s-30s into the interview, the male spouse, armed with a handgun and training ammunition, banged on and entered the room’s rear door, slammed the door, and started yelling from behind the wall.

After, 10s-15s the male spouse came into view at a distance of 18 feet. With his left hand on his forehead, he concealed a handgun behind his body with his right hand. Without warning the roll player started firing the weapon towards the officer. Once the officer drew his handgun and returned fire with the two bullets in the gun, the researcher blew a whistle and the second trial ended.

Following the second trial, the subject officers were debriefed and then escorted to a garage where they were instructed to conduct a stationary firearm draw. The stationary draw would be used for comparison to their trial performance.


During the trials, startle responses were observed in 20 of the 22 subjects. Startle responses were considered to have started when there was an observed reflex (e.g., neck flexion, arm shielding face, etc.) in the experimental trial. Having equipped the officers with a 15-sensor motion capture system, researchers were able to use computer software to identify and plot precise start and stop times for startle responses.

There were two significant observations from the data. First, 80% of the officers began to initiate their firearm draw before or immediately following the completed startle response. That the firearm draw could be initiated before the startle response was completed was reported as a novel discovery by the researchers. This observation provided evidence that predetermined motor actions can be coupled with the startle response, and that productive defensive action can be initiated before the startle response has been completed. [7]

The second significant observation was that officers were collectively an average of .36 s slower in their draw times during the simulated lethal threat trial as compared to their controlled draw times. However, six of the officers executed their firearm draw performance trials the same or faster than their controlled times!

The Way Forward

The startle response can jump-start defensive movements in response to a perceived threat. The automatic, nonconscious movements drive hands and legs into defensive positions, protect the neck, head, and eyes, and prepare the body to fight or flee.

In the face of imminent physical threats, the startle response can be a useful and necessary reaction. Experts have been training people to couple the startle response with a pre-programmed motor movement. [8] This latest research now provides empirical evidence that motor movements, like the firearm draw performance, can be initiated before the startle response has been completed.

Trainers will continue to explore how to use the startle response to accelerate advanced motor performance. It may not be useful or even possible to completely eliminate the startle response. However, researchers and trainers have been working to mitigate the response where it can impede effective performance. The Federal Aviation Administration trains pilots to avoid or quickly recover from the startle response by anticipating the initiating event and then considering and vocalizing the responsive actions. [9]

In related studies, researchers continue to explore the relationship between the startle response and previous exposure to critical incidents, PTSD, sleep habits, fatigue, genetic predisposition and exposure to a triggering stimulus.

For police, the ability to anticipate and identify the potential for sudden attacks in various settings may also mitigate the startle response and enable effective responses. In other words, expect the unexpected and have a practiced plan.


1. A reduced risk was recognized when the vehicle impaired the shooter’s view of the officer or impaired their ability to effectively align their weapon against the officer.

2. Davis M. The mammalian startle response. Neural Mechanisms of Startle Behavior.1984;287-351.

3. Id.

4. Michael Kantor, Department of Research and Sponsored Projects, Rocky Mountain University of Health Professions, Provo, Utah, United States of America; Dane Bartz, School of Nursing and Health Sciences, Saint Xavier University, Chicago, Illinois, United States of America; Division of Research, Robert Pettitt, Department of Health Sciences, Salt Lake Community College, West Jordan, Utah, United States of America.

5. Jason, A. Shooting Dynamics: Elements of Time & Movement in Shooting Incidents, Investigative Science Journal Vol.2, No.1, January 2010; Sandel WL, Martaindale MH, Blair JP. A scientific examination of the 21-foot rule. Police Pract Res. 2021; 22(3):1314-1329.

6. Speeds are expected to vary as a result of variables that include the skill of the officer, type of holster and type of weapon, etc.

7. In this study, .59 seconds from the start of the startle response (or 76% into the startle response) some officers started to initiate the firearm draw performance.

8. See Tony Blauer at

9. FAA Startle Response Safety Minute training video.

About the author

Lewis “Von” Kliem, MCJ, JD, LLM, has worked as a civilian police officer, attorney, educator and author. Von is the executive editor of Force Science News and co-owner of Von Kliem Consulting, LLC, where he trains and consults on constitutional policing, use of force analysis, crisis communications and trauma-informed interviewing.

The FSRC was launched in 2004 by Executive Director Bill Lewinski, PhD. -- a specialist in police psychology -- to conduct unique lethal-force experiments. The non-profit FSRC, based at Minnesota State University-Mankato, uses sophisticated time-and-motion measurements to document-for the first time-critical hidden truths about the physical and mental dynamics of life-threatening events, particularly officer-involved shootings. Its startling findings profoundly impact on officer training and safety and on the public’s naive perceptions.