Force Science Study Update – Can cops avoid “extra” shots & resistance/UOF affect accuracy of sobriety testing


I. Can cops really avoid “extra” shots? A realistic research review

A flashpoint of controversy in some officer-involved shootings is when officers do not immediately cease fire the moment a deadly threat ends and they are no longer in mortal danger.

An officer’s ability to instantly stop pulling the trigger once a “stop shooting” signal becomes evident is not always considered. Instead, the officer behind the gun may face harsh media criticism and daunting legal action alleging deliberate excessive force for firing “unnecessary” extra rounds.

This is a conundrum that the Force Science Institute has explored in pioneering research, and a review of its findings is published in the current issue of Law Enforcement Executive Forum, a peer-reviewed journal.

The report, authored by FSI’s executive director Dr. Bill Lewinski, Dr. William Hudson, dean of the College of Engineering, Mathematics, and Science at the University of Wisconsin-Platteville, and Jennifer Dysterheft, a Force Science research associate and doctoral candidate at the University of Illinois, focuses primarily on four human-perception, decision-making, reaction-time experiments conducted with 102 experienced LEOs in Arizona.

“Our findings, obtained under stressful but nonthreatening laboratory conditions, comprise a starting point for understanding the human dynamics involved in promptly concluding a shooting episode,” Lewinski told Force Science News. “They very clearly illustrate the challenges of responding instantaneously to a rapidly changing situation.

“The infinitely more complex circumstances of a real-world, life-threatening gunfight are likely only to magnify what our officer volunteers experienced.”

LIGHT CUES. In the experiments, the officers one at a time were equipped with nonfiring 9mm Glock training guns that were rigged so that trigger pulls could be precisely timed to thousands of a second. In a training room, they then faced a 3X3-ft. “stimulus board” studded with nine clusters of colored LED lights that could be remotely activated by computer in unpredictable patterns of increasing complexity. Each officer responded with five “trials” to each of a series of four tests as monitors measured their trigger-pull reaction times.

Test #1. To establish a simple typical reaction time, officers were instructed to watch a specific cluster of lights on the board and when a green light came on, they were to pull the trigger once, “as quickly as possible.”

The fastest time between the light flashing on and an officer beginning to move the trigger was 0.17 second, with the slowest being half a second. The average time to perceive the change cue and initiate trigger pull was 0.25 second. This is starting with the officer’s gun already aimed at the threat, with the officer’s finger on the trigger and the officer primed to respond.

Test #2. For these five trials, the officers were told to begin “shooting” as quickly as possible when the green light came on and to “continuously pull the trigger” as they might in an actual gunfight until the light blinked off, representing an end of threat. Then they “must stop instantly” or their “score” would be penalized. The duration of the shooting time was randomly varied among the trials.

Responding to this simple stimulus, some officers were able to stop immediately, but the slowest to stop completed six more trigger pulls after the light went off before releasing the trigger for good. On average, officers shot one more round and started a second trigger pull that would likely be completed in a real-world situation after the “threat” stopped.

Test #3. Officers were to watch a full row of light clusters, which consisted of three bulbs each. If only one or two lights in a cluster came on, the officers were not to shoot. Only when a complete cluster was simultaneously illuminated were they to fire.

This relatively simple increase in the complexity of decision-making roughly doubled reaction times. Now, on average, 0.56 second passed between the time a full cluster lit up and the officers initiated a trigger pull.

Test #4. In the final and most complex trials, officers were to focus on the entire stimulus board. They were to pull the trigger “as quickly as possible” once all the green lights in any row were lit. As distractions, yellow and red lights in the clusters might turn on or the green lights in a row might not all be lit.

The average reaction time to start shooting–0.46 second–actually improved slightly for this experiment. The officers learned to “anticipate a pattern evolving and simply had to recognize that pattern,” the researchers explain.

IMPLICATIONS. The decision-making in the experiments was the “simplest possible” compared to the challenges facing officers in real-world deadly force encounters, the researchers point out. In street confrontations, LEOs must deal with “a multitude of stimuli; ambiguous circumstances; poor ambient light; and a complex, dynamic, and often evolving threat situation”–all of which will tend almost inevitably to impact on an officer’s ability to rapidly evaluate options and react to contextual changes.

“It is always expected that officers perform at expert levels of shooting,” Lewinski says. “If they fire excess rounds or make any mistakes, they are highly criticized and held accountable. Yet this study suggests, among other things, that many officers may be unable to cease firing instantaneously when the suspect is no longer a threat.

“Everything an officer does takes time. It takes time to perceive that a threat level has changed and it takes time to decide to stop shooting and to mechanically activate that decision. When officers are engaged in continuous rapid fire, as their training requires for defending their lives, the stopping process is more complex and generally takes longer.”

In their paper, the researchers note that “if an officer were to take [merely] 0.56 seconds to react to a stop-shooting signal, three to four [extra] rounds could be fired by the officer as an automatic sequence after the signal to stop had already occurred.” The slower an officer’s reaction time, “the greater number of shots [can] be fired before a conscious stopping can occur.”

The researchers also comment on the number of mistakes officers made during Tests #3 and 4. In Test #3, 3% of rounds fired were “false positives”; that is, officers misread the stimulus and fired when they shouldn’t have. “That number more than doubled [to 8%] with the addition of pattern recognition” in Test #4.

“This directly translates into officer-involved shootings, suggesting that with complex decision-making components, in addition to movement patterns, there is nearly a 10% risk of officers making false positive errors or shooting when the pattern appears to represent an evolving threat but in reality it never reaches that point.”

What suggests even more physical danger for officers is the number of false negatives that occurred in the tests, “when the officers did not shoot when they should have.” This represented only 1% of the trials in Tests #3 and 4, but on the street the consequences could have been grave, giving “deadly suspects the advantage” and putting officers’ “lives at risk.”

Among other troublesome aspects of “extra shots” incidents, the researchers also address controversial complications that often arise from rounds fired at moving vehicles and at suspects who are falling to the ground after already being hit.

“Before analyzing real-life shootings, it is necessary to understand the basic reaction times and other data recorded in this study,” Lewinski says. “The principle purpose of the study was to create a foundation of such knowledge. We anticipate conducting more sophisticated testing of pattern recognition and decision-making in the future.”

The full study, titled “Police Officer Reaction Time to Start and Stop Shooting: The Influence of Decision-making and Pattern Recognition,” will soon be available on the journal’s website as well as on the Force Science Institute site. We will make an announcement once the study is posted.

The study findings and their implications for investigators and use-of-force reviewers are discussed in detail during the five-day certification course in Force Science Analysis.

II. Do resistance & use of force affect accuracy of sobriety testing?

Will a foot chase, a physical struggle, or the use of non-deadly force on a drunk-driving suspect affect his ability to perform field sobriety testing accurately?

The suspect’s lawyer might like a judge or jury to think so–but findings from a new, first-of-its-kind study suggest otherwise.

The study, led by Dr. Jeffrey Ho of the Hennepin County Medical Center and the Meeker County SO in Minnesota, was inspired by a court case in New York State involving a driver who was stopped for speeding and subsequently fled on foot in an effort to avoid arrest for suspected OWI (operating [a vehicle] while impaired).

During apprehension, the suspect received a six-second CEW exposure to the back. Several minutes later, he totally failed a standardized field sobriety test (SFST). At trial, his lawyer blamed the failure on “lasting neurocognitive and psychomotor impairment” caused by the CEW, despite a “significant amount” of alcohol in his system.

Ultimately this gambit was unsuccessful, but, Ho writes, it “did initiate the question of whether or not a suspect’s resistive actions or a LEO’s use of force…could alter the result of the SFST.”

5 COMMON STRESSORS. Using 57 LEO and CO volunteers from a police training facility in Arizona, Ho’s team tested SFST performance against five stressors that commonly occur on OWI stops.

First the subjects, mostly males and ranging in age from 19 to 55, were given a full- battery field sobriety test, including horizontal gaze nystagmus, walk and turn, and one-legged stand, as a baseline marker.

Then they were randomly assigned to play the part of a resister in one of five scenarios:

• a five-second TASER X26 CEW exposure, with probes deployed to the back from about seven feet away;

• a 100-yard sprint to simulate a foot pursuit, with a tight S-curve weave in the middle and a five-yard crawl at the end;

• a 45-second fight against a padded opponent, in which they were “encouraged to punch, kick, push, and use elbow and knee strikes” while being physically harassed, blocked, and pushed during constant contact;

• a hide-and-seek exercise with a K-9, in which the dog ultimately chomped onto the volunteer’s padded arm for 20 seconds while the “suspect” tried to shake him off;

• a stream of 10% OC spray to the face and neck (with eyes shielded by swim goggles), followed by a 90-second decontamination process.

Once the assigned scenario was completed, each volunteer was again given the full SFST.

RESULTS BEFORE & AFTER. During the pre-scenario field testing, three volunteers “stepped off the line once” during the walk-and-turn component, resulting in a single penalty point given each of them.

After the stress scenarios, however, “no subject received penalty points for any factors of the SFST,” Ho reports. A few complained of dizziness, lightheadedness, vomiting, or minor abrasions from falling during the scenarios, but all were capable of performing the sobriety tests and all passed with perfect scores.

“Our study suggests that significant suspect resistance, fleeing, or the application of common LEO force options [do] not deteriorate SFST screening accuracy when performed 10-15 minutes after the resistance, fleeing, or use of force event…. [W]e also did not find any correlation with stress from resistance, fleeing, or use of force…causing neurocognitive or psychomotor impairment that would prevent a person from participating accurately in a SFST.”

Although the subjects were not tested “against every possible physical or emotional stressor” that could be present in an OWI stop, the study has “important implications for LEOs in the field and legal professionals in the justice system,” Ho writes. “It should reassure LEOs to know that they can rely on their training, experience, and the validity of the SFST even…where resistance, fleeing, or use of force has occurred.”

The full study, titled “Effect of simulated resistance, fleeing, and use of force on standardized field sobriety testing,” appears in Medicine, Science and the Law, the official journal of the British Academy for Forensic Sciences. A free abstract is available at: http://msl.sagepub.com/content/early/recent.

Our thanks to Atty. Michael Brave, National/International Litigation Counsel to TASER International, Inc., for alerting us to this study. Dr. Ho serves as medical director to TASER International, and another member of the research team, Dr. Donald Dawes, is a medical consultant to the company. Ho can be reached at: hoxxx010@umn.edu