The small story in the Philadelphia Daily News in 2010 was an ordinary police scanner report.

It recounted how a 56-year-old man, acting erratically and holding a knife, was repeatedly shocked by a stun gun* and then shot and killed by police officers on a side street in North Philadelphia. According to the report, the police used fatal fire after the man failed to respond to the shock and “charged” an officer.

Witnesses, however, expressed different accounts of the event. Some said that the man, a grandfather and veteran named Harry Bennett with a history of mental illness, had posed no threat and that the stun gun had appeared to deliver a jolt: One witness believed it had caused a kind of paralysis and that Bennett seemed unable to respond to orders, including one to drop the knife, before he was shot.

The story — just one incident out of thousands involving stun guns each year — raises questions about the devices, which deliver a high-voltage electrical shock to temporarily disable a subject.

Had the gun really failed to work? How could the police be sure? Was it possible that the electrical shock itself affected the man’s behavior?

Shock Troopers
In the more than two decades since law enforcement agencies began adding stun guns to their arsenals, police have used Tasers, the most prevalent brand, on humans some two million times, according to Taser International’s statistics. About 16,000 American police departments now use the devices, up from 10,000 only a few years ago.

Yet despite widespread adoption by law enforcement, much is unknown about exactly how the shocks affect individuals in police encounters fraught with complexity, stress and danger.

The dearth of information on the subject inspired Drexel Criminal Justice Program Director Robert J. Kane to ask a question with potentially broad implications for the criminal justice system: What does a 50,000-volt shock do to an individual’s ability to reason?

Last spring, Kane, along with three researchers at Arizona State University’s (ASU) School of Criminology and Criminal Justice — Associate Professor and co-principal investigator Michael D. White, Assistant Professor Justin D. Ready and graduate student Lisa M. Dario — designed a safe test that they say constitutes the first randomized controlled test, ever, of the cognitive effects of being shocked with an electric stun gun. The study was funded by the National Institute of Justice and the U.S. Department of Justice.

Specifically, the team was curious to learn whether receiving an electric shock from a Taser might affect the ability of a suspect to understand and rationally act upon his or her legal rights. (Taser-branded devices were used for the experiments and two of the company’s emergency room physicians served on the research team’s advisory board.)

As anyone who’s seen a TV cop show knows, police making an arrest are required to read the suspect a “Miranda” warning, named for the 1966 Miranda v.  Arizona case requiring police officers to inform suspects in custody of their Constitutional rights against self-incrimination — immortalized in the well-known phrase “you have the right to remain silent.”

But despite the ubiquity of Miranda warnings in popular culture, Miranda warnings themselves vary widely in content and intelligibility: Some warnings are read at second-grade level, while others show up on reading-level tests as graduate-level language. What’s more, the Constitutional rights they safeguard tend to be poorly understood in general, and are often waived by suspects who don’t fully understand what they’re doing — decisions that can have profound impact on an eventual judicial finding of guilt or innocence.

A 2010 study by researchers from the University of North Texas, the Harvard Medical School and Southern Methodist University’s Dedman School of Law found that college students and actual criminal defendants were about equally bad at correctly answering questions on a quiz about their rights in an arrest.

“Not only do they not know” their rights, says Dr. Richard Rogers, the University of North Texas professor of psychology who led the study, “but there are gross misconceptions.”

Moreover, police have been encouraged to use stun guns in lieu of firearms particularly in cases when officers encounter suspects who are mentally ill, in the throes of a psychotic episode or under the influence of drugs — where a person’s understanding of their rights might already be fragile.

Demographic statistics on stun gun use are hard to come by, but one 2011 study by the New York Civil Liberties Union found that 40 percent of stun gun incidents it reviewed from around the state involved “at-risk” subjects including the elderly, children and the mentally ill (the last category made up one-third of the incidents).

Kane and his colleagues wondered what the presumably traumatic effects of being shocked would do to that already-poor understanding.

“If you are exposed to a Taser and the cops [arrest] you, 10 or 15 minutes later, do you have the same cognitive ability to knowingly waive your rights?” Kane explains.

The Drexel/ASU team recruited 142 students from Arizona State University and divided them into four groups. Half of the students received five-second shocks, and half did not. To simulate the heightened physical state one might expect in a tense police encounter, half of each of the groups also spent time hitting a punching bag.

The researchers took a number of safety precautions: Subjects were screened for health issues and any drug use or intoxication, and the trials were conducted at a hospital, with nurses on hand throughout the trial.

But Kane doesn’t quibble when it comes to the act itself: “We caused these students a great deal of pain,” he says. For that reason, he expects the study will draw a fair amount of attention, or possibly even fierce criticism, when it’s published.

“There are scientists out there who believe we have acted unethically,” Kane says. “But we believe very strongly that there is a moral imperative here… Police have Tased over one million people in America [another million officers were exposed to Tasers during training], and until now we had no idea about what this thing does to their ability to make decisions.”

At six different stages before and after being shocked (or not, in the case of the control group), the students were asked to take a battery of cognitive tests, among them the three-part Hopkins Verbal Learning Test. The test is widely used to identify everything from mild learning impairments to dementia by measuring a person’s ability to learn new information (a string of words) and then recall that information after different intervals of time. The Hopkins test was the closest thing they could think of, Kane says, to a Miranda warning scenario, in which suspects are expected to understand their rights and act upon that understanding in a short time.

Some of the cognitive tests didn’t show much of a change. But when it came to the Hopkins Verbal Learning test, cognitive ability among groups that received the shocks “decreased substantially” in the first hour or so afterward — so substantially that some students’ scores on the tests shortly after a stun gun shock registered at levels that can be classified as “dementia.”

The students who received shocks showed the most trouble in the “delayed recall” portion of the Hopkins test, says ASU’s Ready.

“I would read off a list of words, then do a bunch of other tests, and then I would ask them to repeat the words,” he says.

Students who had been shocked were noticeably worse at remembering those words than when they took the same test an hour earlier, and their scores declined substantially compared to the control group.

“We had people who scored zeroes,” Ready says.

Overall, students’ cognitive scores dropped an average of five points on the Hopkins test to a score of 21, falling between a normal score of 26 and a classification of “mild cognitive impairment” at 18.

After an hour, the effect seemed to wear off, and students’ scores returned to normal when they were tested the next day.

“These were college students — used to taking exams, remembering things and writing stuff down,” Kane points out. “You wonder what the results would be among a more representative population.”

Parting Questions
The findings raise a critical question for police and the courts, says David Weisburd, a professor of criminal justice studies at George Mason and Hebrew universities who published a pilot study by the researchers (using volunteer police officers as test subjects) in the Journal of Experimental Criminology, which he edits.

“Can a person who is [shocked by a stun gun] be seen as responding to police requests in a way that meets legal requirements?” he asks.

The new findings, he says, suggests that maybe they can’t. “This is critical information.”

The Drexel/ASU team’s work could eventually affect police practices, says Geoffrey Alpert, a professor of criminology and expert on police practices at the University of South Carolina. He conducted a three-year study of stun gun use by police officers that found, in a nutshell, that officers often use them “too early and too often,” as he puts it.

“It’s a really important point,” says Alpert. “A lot of people have looked at [stun gun]-related deaths, but no one has really thought about cognitive issues. […] When do you interview a witness? That’s a big question. Policy-wise, maybe it’s important to wait a little bit.”

As the researchers prepare the study for publication, Kane and ASU’s White are planning a follow-up study focused on how or why certain “sub groups” within the study were more susceptible to the effects of the shocks than their peers.

“There’s a lot of variation” within the findings, Kane says. Among those whose cognitive scores dropped after being shocked, “some scored 12, some scored 18, some didn’t drop much at all.”

As for the use of human subjects, Weisburd says he expects the study will cause a stir.

“[The study] raises the question of whether it is ethical to cause potential harm to someone, to answer the question that they try to answer. On the other side, how are we to gain answers that are important to society if we cannot carry out experiments like this?” he asks. “I don’t have an answer to this conundrum.” 

“I imagine,” Kane says, “that this might find its way into ethics textbooks.”