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January 06, 2014
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Force Science Institute Destroying Myths & Discovering Cold Facts
with Force Science Institute

Does TASER deployment on a subject cause ‘mental impairment’ with legal ramifications?

Prosecutors and police attorneys may find a new study useful in countering the assertion that a TASER “ride” messes with the mind to a unique and significant degree

When a suspect tried to rabbit on foot from a drug interdiction stop in Louisiana and then refused to follow commands after officers caught him, he was zapped with a TASER three times before being successfully handcuffed — once via a probe to the arm and twice in drive-stun mode to the leg, for a total of 16 seconds. 

Soon after, he twice confessed to knowingly transporting “a significant quantity of cocaine” from Texas, intending to package and sell it in New Orleans. 

In federal court, however, the suspect argued that his admissions should be thrown out on grounds that the TASER-ing had “mentally impaired” him to the point that he was “unable to understand” his Miranda warning and the “ramifications of waiving” his right to remain silent. 

The judge ruled against him, noting, among other things, that the suspect did not buttress his argument with any scientific data showing that a TASER-ing produces incompetence “for any amount of time.” 

Still, other defendants have made the same impairment claim and others may do so in the future. Prosecutors and police attorneys may find a new study useful in countering the assertion that a TASER “ride” messes with the mind to a unique and significant degree. 

In truth, the researchers report: 

•    The overall cognitive impact of a TASER exposure is so slight and so brief that it's of “questionable clinical significance”
•    Subjects who've been TASER-ed have no trouble understanding and following instructions
•    Indeed, subjects recovering from a TASER exposure tend to score better on one important cognitive measurement — a test of accuracy — than subjects who have experienced some other types of force or arrest-related stressors

A 10-person team authored the study, headed by Dr. Donald Dawes, an emergency medicine physician, reserve officer/SWAT tac doc with the Santa Barbara (CA) PD, and a well-known expert on conducted electrical weapons (CEWs). The group's report, titled “The neurocognitive effects of simulated use-of-force scenarios,” was recently published online by the journal Forensic Science, Medicine, and Pathology. To read an abstract free of charge and to gain access of the full study for a fee click here 

A Troublesome Void
“While the physiologic effects of modern conducted electrical weapons (CEWs) have been the subject of numerous studies, their effects on neurocognitive functioning...are less well understood,” the researchers write. “This void...has been exploited in civil and criminal actions with claims that [include] an inability to follow an officer's commands, perform a field sobriety test, or understand Miranda warnings post-exposure due to...neurocognitive impairment,” either short- or long-term. 

Hopeful of filling the void, the researchers set out to determine not only the mental impact of TASER deployment but also how that effect, if any, compares with the results of “other use-of-force options [and] arrest-related stressors.” This effort became the first time such a comparison has been made. 

Stress Exposure
​At a police and fire training facility in Arizona, the researchers assigned a pool of 56 LEO and CO volunteers, ranging in age from 19 to 55 and mostly males, to experience one of five test exercises. In roughly equal numbers, the volunteers underwent: 

1.) a five-second probe-shot to the back from an “off-the-shelf” TASER X26 at a distance of 7-10 ft.; 
2.) a 100-yard, “maximal effort” sprint through an obstacle course, simulating a foot chase, with a 15-ft. crawl at the end
3.) a 45-second simulated fight, consisting of “maximal” punches and kicks against a heavily padded instructor
4.) a K-9 search-and-bite exercise while wearing a full-body, protective bite suit, with the dog maintaining an arm bite for 20 seconds as the targeted subject tries to shake him off
5.) a spray of 10 percent OC to the face and neck with eyes shielded by swim goggles (to preserve vision for the cognitive testing that followed).

Baseline neurocognitive measurements were taken before these stress/force exercises and were repeated immediately afterward and again at intervals of 15 minutes and one hour. 

For this testing, the volunteers completed three portions of an extensive computer-based program used for evaluating cognitive impairment after combat-related traumatic brain injuries. Specifically, the testing measured visual scanning, processing speed, attention, learning, spatial discrimination, reaction time, accuracy, and memory. 

Pre- and post-exercise vital signs were also taken. 

Cognitive Outcomes
Other research has shown that cognitive performance may decline immediately after exposure to major stress and then “tend[s] to recover rapidly.” Generally, that proved true in the Dawes study as well. 

One exception was reaction time. On average it slowed slightly (by about 150 milliseconds) among participants in all the test exercises and did not return to baseline within an hour. 

The largest negative cognitive impact, though, was on memory. Again, the deficit persisted past the last measurement, administered an hour after the stress exposure. This suggests that “working memory may be the most sensitive to use-of-force stress,” with deficits deepening as stress rises during an arrest situation, the researchers write. 

In terms of impact on vital signs (blood pressure, heart rate, etc.), the most stressful exercises proved to be the simulated fight and the simulated flight. 

Overall, the study team found that cognitive skills held up well across all the various stressful exercises, including the TASER exposure. The subjects, they report, “could follow directions quite well immediately after the...scenarios, moving to the various stations...as directed, keeping track of their time...without difficulty, and were able to sit and take the...battery [of cognitive tests]. 

What mental impact occurred was overall “transient, of questionable clinical significance, and similar” across all the stressors, the team writes. In general, “We did not find a significant difference between the various used-of-force scenarios in terms of neurocognitive functioning.” 

For one cognitive factor — accuracy — subjects who had been TASER-ed actually performed better than most others, maintaining their baseline levels even after CEW exposure. (The same was true of officers in the dog-bite exercise, although the team acknowledges that without the protective padding the K-9 attack would have been considerably more stressful!) 

Legal Implications
The researchers believe this study “is legally significant in that it establishes that the use of CEWs causes no greater decline in neurocognitive performance than any of the alternative means of subject resistance or control evaluated” and common to the street. 

“Our data...could be useful in legal cases in which [attorneys] attempt to argue that a specific use of force caused a [persistent] neurocognitive deficit.” 

The legal arena being what it is, though, the researchers realistically predict that “more study and debate” will ensue over the use of force and cognitive impairment related to “Miranda rights, performance of field sobriety tests, giving of statements, consent to search, or other action requiring voluntary, knowing, and intelligent waiver or consent.” 

Meanwhile, the researchers suggest that in theory “it could be optimal to wait” at least 15 minutes after a significant use of force before presenting a suspect with “complex neurocognitive tasks.” But in the real world, given the team's findings, that may be “an unnecessarily conservative recommendation.” 

Finally, the study group acknowledges that on the street, confrontations are often “confounded” by multiple uses of force, the influence of drugs and alcohol, and “the stress of the consequences of being arrested.” 

Consequently, “This limits the ability to generalize our findings to these more complex scenarios. However, we feel that our [work] offers some baseline data that can help with the understanding of these complex encounters.” 


About the author

The Force Science Institute was launched in 2004 by Executive Director Bill Lewinski, PhD. - a specialist in police psychology -- to conduct unique lethal-force experiments. The non-profit Force Science Institute, 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.

For more information, visit www.forcescience.org or e-mail info@forcescience.org. If you would benefit from receiving updates on the FSRC's findings as well as a variety of other use-of-force related articles, please visit www.forcesciencenews.com and click on the "Please sign up for our newsletter" link at the front of the site. Subscriptions are free.





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