When someone is shot with a Taser, a stun gun used by police departments around the country, about 50,000 volts of electricity are sent through two wires into barbs stuck in the person’s skin. The pain from this is often intense enough to knock down targets without killing them (although they are at risk of fatal head injuries). While the physical effects can heal, new research shows these weapons can have a more profound effect on a person’s cognitive function.

Published in Criminology and Public Policy, the new study from Drexel University and Arizona State University found participants who were shocked experienced short-term cognitive decline similar to dementia. This in turn hampered their ability to understand their Miranda Rights, the "right to remain silent" warning given to every suspect upon arrest, and led researchers to question whether people who are tased are at risk of waiving their right to a fair (or at least clear-headed), interrogation.

"The findings of this study have considerable implications for how the police administer Miranda warnings," said lead author Dr. Robert J. Kane, of the Criminology and Justice Studies Department in Drexel's College of Arts and Sciences, in a press release. "If suspects are cognitively impaired after being tased, when should police begin asking them questions? 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? We felt we had moral imperative to fully understand the Tasers' potential impact on decision-making faculties in order to protect individuals' due process rights."

The study involved 142 volunteers from Arizona State, split into four groups: Control, which did nothing; punching bag, where volunteers hit a bag to simulate the intensity of a violent police encounter; Taser, where they were shocked for five seconds; and punching bag and Taser, which involved hitting the bag and getting tased for five seconds. After these tasks were completed, participants were asked to complete a battery of tests on four separate occasions to test their cognitive function: Immediately after the task, an hour later, three days later, and a week later.

The highest levels of variance for the participants appeared after taking the Hopkins Verbal Learning Test (HVLT), a test normally used to assess cognitive disorders ranging from learning impairments to dementia. It asks subjects to read 12 words out loud, then recall them in any order at various points in time. Before the experiments, participants scored an average of 26 on the test, which is above the national average. However, immediately after getting shocked, 25 percent of participants scored lower than 20, putting their cognitive function in line with that of a 79-year-old person.

Administrators of the test could also “clearly observe the difficulty many participants had with the HVLT after Taser exposure," said co-author Dr. Michael D. White, a professor in Arizona State’s School of Criminology and Criminal Justice, in the press release. His team noted these are only short-term effects, and that most effects of being tased wear off after about an hour.

Aside from disrupting the memory of participants, the researchers found being tased made concentration difficult, anxiety levels rise, and left the participants feeling overwhelmed. "Being shocked had a traumatic effect on some participants," said Kane. "Some were emotionally debilitated by the experience."

Because the experiment was somewhat cruel, the researchers were quick to point out volunteers were all young, seemingly healthy people who had passed a multitude of tests to even be considered for the honor of getting tased for science. They said this is likely in stark contrast to the people who find themselves at the receiving end of a police officer’s Taser — those who are drunk, high, or mentally ill.

"We would expect 'typical' suspects — who may be high, drunk, or mentally ill and in crisis at the time of exposure — to experience even greater impairment to cognitive functioning as the result of Taser exposure," Kane said.

Thus, Kane suggested people who are Tased “may be unable to understand and rationally act upon his or her legal rights.” They may also be more likely to waive their Miranda rights “directly after Taser exposure, or give inaccurate information to investigators. These decisions can have profound impact on an eventual judicial finding of guilt or innocence.”

Public discourse regarding the best way to use a Taser in everyday policing may best protect both police officers and their suspects, the researchers said (after all, one is innocent until proven guilty). One potential way to do this is to have police wait at least an hour for the effects of the Taser to wear off before beginning an interrogation.

Source: Kane R, White D. TASER Exposure and Cognitive Impairment: Implications for Valid Miranda Waivers and the Timing of Police Custodial Interrogations. Criminology & Public Policy . 2015.