Force Science News #244:

Does Tasing cause "mental impairment" with legal ramifications?

In this issue:


I. Does Tasing cause "mental impairment" with legal ramifications?


II. From our in-box: Our readers write...


III. Sprint study now available in full online


I. Does Tasing cause "mental impairment" with legal ramifications?


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 Tasing 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 Tasing produces incompetence "for any amount of time."


Still, other defendants have made the same impairment claim and others may do so in the future. So 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 Tased 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:


a five-second probe-shot to the back from an "off-the-shelf" TASER X26 at a distance of 7-10 ft.;

a 100-yard, "maximal effort" sprint through an obstacle course, simulating a foot chase, with a 15-ft. crawl at the end;

a 45-second simulated fight, consisting of "maximal" punches and kicks against a heavily padded instructor;

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; or

a spray of 10% 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 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 Tased 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."


[For more information, Dr. Dawes, a consultant to TASER International, Inc., can be reached at: Two other members of his team, Dr. Jeffrey Ho and Atty. Michael Brave, also have TASER affiliations. The study was peer-reviewed by scientists without TASER connections.]


II. From our in-box: Our readers write...


Officer's right to counsel in post-shooting criminal investigation

Regarding our report on the book When Cops Kill [see FSN #238, 9/11/13]:


The author claims that after a shooting, because an officer is being interviewed in a potential criminal case, he or she is entitled to have an attorney present during the interview. However, consider the case of Ward vs. City of Portland [857 Fed 1373 (9th Cir. 1988)].


In that case my former partner was escorted out of the PD because the City declared that even though the officer was being interviewed in a criminal investigation he was not entitled to have an attorney present because there was no indication that the officer had committed a crime. The 9th Circuit reversed a dismissal of the case, which then died a quiet death, since the matter was resolved through collective bargaining negotiations. Still, that train of thought could be adopted by an employer.


John Hoag, police union attorney (ret.)

Instructor, Force Science Analysis certification course

Petersburg, AK


Don't assume a prone suspect means safety for you

Regarding recent study reports and letters from readers about research that challenges the supposed danger of prone positioning [see FSN #240, 10/7/13 and #241, 10/22/13]:


Did those commenting on the prone control study read the same study I did? To me it pointed out that "prone control" is not the "be all and end all" of arrest control techniques it is often touted to be, not that it should be abandoned. Do not assume you are safe because your suspect is proned out. It does not hurt to mix things up a bit and use other means of control given the circumstances.


Dave Bahde, firearms and tactical consultant

Sniper Sustainment and Logistics LLC

Sandy, UT


It's a legal issue, not a medical one

Dr. Christine Hall's study is far from the first to suggest that being placed prone is physically neutral. That does not mean we should abandon the warning to avoid the technique.


The real reason to avoid prolonged prone positioning is this: If suspect dies when he has not been left in the prone position, that's one less "arrow" the plaintiff's attorney can fire at the officer involved. In excited delirium classes, I always teach that not leaving a suspect proned out is a legal warning, not a medical one.


Jerry Staton, Training Director

Affordable Realistic Tactical Training

Member, TASER Training Advisory Board

Del Valle, TX


Force findings consistent with earlier research


Regarding Dr. Hall's recent study of injuries in use-of-force incidents in Canada: The Seattle PD conducted a similar study of our force incidents several years ago, with similar findings. The study, done in conjunction with the University of Washington Medical School, covered all use-of-force incidents in a 12-month period. [Ed. Note: The research revealed that significant injuries were rare, that the only deaths were firearms related, and that most hospital admissions were for problems unrelated to the UOF.]


The study was published in the Journal of Trauma Injury, Infection, and Critical Care, Vol. 69:5, Nov. 2010, under the title, "Use of Force by Law Enforcement: An Evaluation of Safety and Injury," with Dr. Jared Strote as lead author.


Mimi Walsh, strategic advisor

Office of the Chief of Staff

Seattle (WA) PD


III. Sprint study now available in full online


In Force Science News #239, sent on 9/25/13, we reported on a study in which a Force Science research team measured the sprinting capabilities of civilians and the implications those findings have for officers in close-quarters contact with aggressive suspects.


That study has now been published in the International Journal of Exercise Science and can be accessed in full at no charge by CLICKING HERE or by visiting



© 2017 Force Science Institute Ltd.