New Study Sparks Debate Over Tasing, Brain Function, & Miranda

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Does the shock from a conducted energy weapon impair a suspect’s brain function to the point that he or she may not properly respond to a Miranda warning?

A CJ research team raises that question in reporting new findings that a person’s cognition suffers significantly for a short period after a CEW exposure.

Their evidence is not sufficient to “call for a national policy” on post-CEW procedures, the researchers concede, but their report suggests that waiting “60 minutes before interrogating suspects who were exposed to a TASER” may be prudent.

Some TASER experts, however, argue that the new study is far too narrow and flawed and that the authors have greatly overstated the relevance of their conclusions.

The study was conducted by Dr. Robert Kane, professor and department head of criminology and justice studies at Drexel University in Philadelphia, and Dr. Michael White, a CJ professor at Arizona State University and associate director of that school’s Center for Violence Prevention and Community Safety. Kane and White are co-authors of the book, Jammed Up: Bad Cops, Police Misconduct, and the New York City Police Department.

Their study, funded by the DOJ’s National Institute of Justice and published in the journal Criminology & Public Policy, can be accessed in full without charge. Click Here to download a copy.

Noting that most CEW research has focused on effects of shocks on the heart, Kane and White wanted to explore “whether the device impairs a person’s cognitive functioning and, if so, whether that impairment may be severe enough to threaten the ‘voluntary, knowing, and intelligent’ requirements for a valid Miranda waiver.”


The researchers’ testing involved 142 healthy volunteers “who passed rigorous screening protocols” to assure they were sober, drug-free, and clear of any mental or medical problems. Drawn from a campus population, nearly two-thirds were white and about a quarter were black or Hispanic; over three quarters were male; and 95% were in their late teens or early 20s.

Randomly they were divided among four “experimental conditions”: Control (who experienced no “intervention”), Exertion (who punched a heavy bag “vigorously” for 30 seconds to “mimic resistance against police”), TASER (who received a five-second CEW exposure from certified police instructors, while face down on a mat in a laboratory setting), and TASER+Exertion (who hit the bag first, then were Tased). The CEW exposures were not across the head or near the brain.

Each participant “completed a battery of valid and reliable neurocognitive tests” at five different times: an hour before their experimental event, immediately afterward, and then an hour, a day, and a week later.

These tests, the researchers say, objectively measured “a range of cognitive dimensions, including auditory recall, verbal learning and memory, visual [perception], speed of processing, mental flexibility, and motor function.”

Before and after the experiments, the volunteers were also asked to subjectively rate their personal “difficulties” with memory and concentration.


The objective tests showed that there were “no significant differences in cognitive functioning” between the four groups before their experimental exposures, Kane and White report.

However, the researchers write, the results indicate that “TASER exposure led to significant and substantial reductions in (a) short-term auditory recall and (b) abilities to assimilate new information through auditory processes.” This disruption of memory and the ability to “assimilate and synthesize new information,” which lasted up to one hour before returning to normal, was “considerable,” they write.

In the initial baseline testing, all the volunteer groups averaged “just above the normal range [of cognition] for healthy young adults.” But immediately after being Tased, approximately one-quarter of each of the two TASER-CEW groups showed a decline in cognitive function to a level expected for 79-year-old non-demented adults–that is, “within the range of mild cognitive impairment.”

Only one-fifth of each CEW group performed at or above the pre-exposure average. In some test results, the average score in the CEW groups declined by more than 30%, the researchers note, in stark contrast to the Control and Exercise-only groups, which “did not change significantly.” This is “both statistically significant and clinically important,” Kane and White assert.

In addition, CEW exposure “caused significant negative change” in the volunteers’ subjective self-assessment. Immediately post-shock, they reported higher levels of difficulty with concentration, anxiety, and feeling overwhelmed, although these reactions began to dissipate quickly.

So, too, did the objective measurements of decline. By the follow-up testing an hour later, scores for learning and memory had returned to baseline levels, “suggesting that the deficits in cognitive functioning [caused by CEW exposure] are short-term.”


Kane and White did not test the volunteers with any reading of the Miranda caution to see specifically what impact a temporary cognitive decline might have on comprehending or waiving the warning. Instead, they evaluated participants’ memory and learning based on the ability to recall strings of unrelated spoken words and numbers. In the researchers’ opinion, this represented “a favorable alternative” to Miranda-specific tests, “at least in an initial study.”

Nonetheless, they claim their findings suggest that “not only might our participants be more likely to waive their Miranda rights directly after TASER exposure, but also they would be more likely to give inaccurate information to investigators.

“Thus, part of our findings implicates a suspect’s ability to issue a valid waiver, whereas another part implicates the accuracy of information he or she might give investigators during a custodial interrogation (e.g., false confessions or statements).”

The researchers raise the specter of innocent parties unable “to process adequately the consequences of waiving their Miranda rights” and thus becoming “susceptible to suggestibility or memory lapses” and making incriminating, inaccurate, or untrustworthy statements “based on short-term memory impairment,” without benefit of counsel.

In one online news story (from Science Daily), Kane was quoted: “There are plenty of people in prison who were Tased and then immediately questioned. Were they intellectually capable of giving ‘knowing’ and ‘valid’ waivers of their Miranda rights before being subjected to a police interrogation?” The study report poses the question: “What would it cost the police under routine circumstances to wait 60 minutes after a successful TASER deployment before administering Miranda warnings and trying to obtain a waiver from suspects?”


In a statement given to Force Science News, TASER International, Inc., manufacturer of the CEW used in the study, charged that Kane and White “make a giant leap by generalizing [their] findings to the broader question of a suspect understanding a Miranda warning. It is very difficult to take a small word-recall score difference (a change of four words out of a series of 36) and generalize that to the understanding of the Miranda warning.”

The company alleges that the study:

  • “over-emphasizes a few measures of those tested and ignores others,” including the fact that “the TASER group showed statistically significant improvements in some of the measures immediately after exposure”
  • “unfairly de-emphasized the fact that the [Exertion-only] group also had decrements in [cognitive] performance,” and that the decline would likely have been even greater had the simulated resistance to police been more realistic than college students punching a bag
  • “over-relies on non-objective self-reporting”
  • “uses a small statistical difference on essentially one of the cognitive batteries to generalize to a statement about understanding consequences.”

Two TASER consultants, Drs. Donald Dawes and Jeffrey Ho, recognized as among the world’s most prolific and prominent researchers of CEW effects, have previously published findings in 2013 related to the impact of CEW exposure on brain function. They agree that shocks from a control device “will cause transient decrements in neurocognitive functioning in the immediate post-exposure period.”

But, they say, their study shows that this is as true of other stressful force encounters, including realistic fighting, running from police, receiving a pepper spraying with an eye shield, and a K-9 bite in a bite suit, as it is of CEW exposure.

Dawes has written: “It is clear that all use-of-force encounters, possibly as well as other arrest stressors separate from force (fear of incarceration, etc.), can affect some areas of neurocognition as part of a generalized stress response. But that stress is not specific to one force option and does not necessarily extrapolate to an inability to understand consequences and the Miranda warning.”

“It is very important to put all this into perspective,” says Atty. Michael Brave, National/International litigation counsel for TASER International Inc. “Imagine the ramifications if officers were required to wait 60 minutes after every encounter involving a stressed person (exertion, emotional distress, agitation, alcohol, drugs, mental impairment, in crisis, etc.) to attempt to acquire any form of consent or waiver (including, but not limited to: Miranda rights, performance of field sobriety tests, giving of statements, consent to search, or other action requiring voluntary, knowing, and intelligent wavier or consent).


In their report, Kane and White clearly state that more research is needed to “assess more accurately the link” between CEW exposure and the informed exercise of Miranda rights. “We recommend a line of research that treats cognitive functioning with the same importance as physical and physiological health with respect to TASER exposure,” they write.

In future testing, they also suggest using an experimental population that more closely mirrors the “typical” suspects likely to be Tased in the field rather than the “healthy, well-educated, sober, and drug-free” subjects recruited for the current study. Suspects who are “drunk, high, or mentally ill and in crisis at the time of [CEW] exposure” will likely experience “even greater impairment to cognitive functioning,” Kane and White speculate.

One “logical next step” is to use actual Miranda warnings–there are nearly 50 different versions in existence–in assessing post-CEW comprehension, says Dr. Michael Smith, director of the Center for Law and Human Behavior at the University of Texas-El Paso.

Meanwhile, Kane and White express the hope that their findings will “initiate a public dialogue” regarding CEWs and cognitive competence during custodial interrogation.

Our thanks to Lt. Glen Mills of the Burlington (MA) PD for first bringing this study to our attention.

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