Earlier this month, Chicago police Superintendent Garry McCarthy announced that his department will launch a pilot program within the next 60 days to test the use of body-worn video cameras. It’s a move that holds promise for greater accountability, but its announcement turned out to be ill-timed: Just two days later, the news about the Eric Garner case broke.

Garner’s death, of course, had received much attention because his last moments—as he gasped, “I can’t breathe”—were captured by a bystander’s cell phone, and the footage was uploaded to YouTube for all to see. But, in the end, a grand jury in New York declined to indict Daniel Pantaleo, the officer who put Garner in an unsanctioned chokehold that killed him.

Understandably, the grand jury’s decision led some to wonder: If the video evidence in Garner’s case couldn’t draw out an indictment, what’s the point? And what good will the new body cameras do for Chicagoans?

The truth is, the body-camera technology hasn’t been around long enough for researchers to come up with any convincing answers. Yet, overall, this hasn’t dampened the enthusiasm for body cameras. The White House has proposed distributing some 50,000 cameras, at an estimated cost of $75 million. The New York Police Department is well on its way to becoming the nation’s largest police force to adopt the technology. And a poll released this month found that an overwhelming majority of the public—nearly nine out of 10—still say they support the use of body cameras. 

As it happens, this paradox is par for the course: When it comes to adopting new technology, the absence of empirical evidence of the benefits is usually not a deal breaker for law enforcement agencies.

Take, for instance, the recording of custodial interrogations. According to the National Association of Criminal Defense Lawyers, Illinois and 18 other states now have rules mandating the recording of interrogations, typically for cases involving homicide or other serious crimes. And an array of local authorities have also embraced the practice voluntarily—out of belief that “recordings prevent disputes about officers’ conduct, the treatment of suspects and statements they made.” 

But things look hazy in terms of empirical evidence. So far, the clearest illustration of the benefits has come from a study in a recent issue of Law and Human Behavior. The study is based on a field experiment in which the researchers set up a hidden camera to film a group of police officers as they interrogated mock suspects. Some officers were told in advance that they were being filmed, but the others weren’t. The researchers found that the officers who knew they were being filmed were less likely to resort to threats or offer false promises of leniency in exchange for a confession.

Jeff Kukucka, the study’s co-author, says his research was the first of its kind to examine the behavior and “decision-making” of police officers in interrogation rooms. As for the paucity of similar empirical research, he chalks it up to the pushback from law enforcement agencies. “Some police departments are not terribly interested in hearing what science has to offer in terms of how to improve the effectiveness of their practices,” Kukucka, a psychology professor at Towson University in Maryland, told me. “Scientists are often seen as outsiders who are challenging the status quo without an adequate understanding of the demands and realities of police work.”

On the use of body cameras, the limited research that’s been conducted so far has come up with a finding similar to Kukucka’s: The benefits might be in influencing behavior before the fact, not providing evidence after it. One of the most cited studies on this comes from Rialto, California, a city of about 100,000 people just west of San Bernardino. During the 12-month experiment, the researchers found that police officers with body cameras were 59 percent less likely to use force than those without. And the police department also saw a reduction in citizen complaints—by a whopping 88 percent.

But the evidence is far from conclusive. For one thing, whether Rialto’s experience could plausibly translate to how body cameras will perform in bigger cities like Chicago is far from clear. Other studies have also shown that recordings do not always lead to universally shared conclusions—with Garner’s case being an Exhibit A—and that the benefits often accrue to the side of police officers. 

And Michael White, a criminology professor at Arizona State University, reviewed five empirical studies, including Rialto’s, for his 2014 Department of Justice report and came away with this conclusion: “Most of the claims made about the technology are untested,” and therefore, “there is not enough evidence to offer a definitive recommendation regarding the adoption of body-worn cameras by police.”

For his part, however, Kukucka says all the hand-wringing over the body cameras’ benefits might be missing a point. “The crux of the issue is whether we are content with denying judges and juries access to information in these recordings that may prove useful to them in rendering their decisions. The alternative … is that they rely on conflicting eyewitness accounts and on he-said-she-said disputes between police and civilians, which—even if video recording isn’t perfect—is undoubtedly an inferior option,” he says. “It all boils down to a relatively simple point—why should we be satisfied with having less information when we could feasibly have more?”