The New York Times reported last week that the New York City Police Department has halted the use of "flashbang" stun grenades. The department began phasing out the devices in 2003 after their deployment in a mistaken drug raid caused 52-year-old Alberta Spruill to suffer a fatal heart attack. The prior year, the department had used flash grenades 175 times.

Flashbangs detonate with a blinding flash of light and a deafening explosion. Their function is to temporarily stun people in a targeted building until police or military personnel can get inside. Though the weapons are marketed as non-lethal, there have been a number of incidents in which they've set homes on fire (some resulting in fatalities), caused severe burns, or confused police officers into thinking they were coming under gunfire, causing them to open fire themselves.

But even when used and executed as intended, flashbangs cause injury by design, and when used by law enforcement, that injury is inflicted on people who have yet to even be charged with a crime, much less convicted of one. In most cases, the crimes that precipitated the raid are consensual and nonviolent: They're drug offenses.

Clay Conrad, a criminal defense attorney in Houston, criminal justice specialist, and author of the book Jury Nullification: The Evolution of a Doctrine, has tried to challenge the use of flashbangs in the service of drug warrants. "It's just an assualt," Conrad says. "These things are designed to blind and deafen. They produce a shockwave of 136 DB or more. You're intentionally injuring people."

In 2008, federal prosecutors indicted three executives at the flashbang producer Pyrotechnic Specialties, Inc. (PSI) for fraud, conspiracy, and money laundering. The indictments came after one of the devices detonated prematurely in a SUV driven by three FBI agents in 2004. A subsequent investigation found that the company knew the devices could detonate prematurely, but covered up the problem.

In November 2008, CNN interviewed the agents about their injuries. One said, "To me, it felt like someone just whacked me in the back with a baseball bat as hard as they could." Another said, "I don't sleep. I have tremendous headaches. I have the doctors claim severe hearing loss, but for all practical purposes, I'm deaf in my left ear." Speaking of the company, another added, "If they could experience that, or someone close to them would have to go through that experience, I'm sure it would be a different story and maybe they wouldn't have allowed it to happen."

The CNN story focused on PSI's fraud and negligence, but what's striking about the FBI agents' accounts is that other than the early detonation, the grenades did exactly what they're intended to do. What the agents experienced is experienced by dozens of people every day who find themselves on the receiving end of a drug raid, where grenades are thrown through bedroom windows, rolled into living rooms, or tossed into hallways. They're being punished—intentionally injurred—before they've so much as seen the inside of a police station. That's before we get to the problem of mistaken raids, and innocent bystanders who happen to be in a home when a raid transpires.

New York City officials aren't the only ones taking notice. In 2008, a judge in New Jersey held a hearing on the use of stun grenades, then tossed the drug charges against a suspected meth offender because state police used flashbangs and paramiltary tactics to serve the search warrant on his home. "This was a commando raid-like scenario," Superior Court Judge James J. Morley said, "and my decision was based on the overall way they approached the case—at 5 a.m. with 29 police officers in commando gear and pointing a weapon at a sleeping 17-year-old." The teen wasn't the suspect. An adult living with him was.

Defense lawyer Clay Conrad's challenge on flash grenades was based on a Texas law that prevents evidence from being admitted in trial if the police committed a crime in obtaining it. He argued in a brief that the initial assault and use of flashbangs constitue a criminal assault. Conrad says the prosecution offered a generous plea before that issue could be hashed out in court. "We were prepared to argue that if these things are as harmless as the state claims, we should be able to detonate one in the courtroom. That would have been fun."

Conrad thinks the use of flashbangs and other overly aggressive tactics may be ripe for a federal challenge. "The argument is that it shocks the conscience," he says. "That argument has some validity to it in the right cases, where you're using these volatile tactics against someone who's suspected of nothing more than drug dealing. It's excessive to the point of violating the Fourth Amendment."

There are certainly scenarios in which flashbangs are appropriate, such as anytime you have someone who presents an immediate threat to the safety of others: bank robberies, hostage situations, or similar sorts of stand-offs. In these cases, the weapons can defuse an already violent situation.

But that isn't how flashbangs are primarily used. Supporters of the devices say they're important for the safety of police officers. We should obviously take sensible precautions to protect cops on the job, but those precautions can't violate the basic rights of everyone else. Flashbang grenades subject people suspected of nonviolent crimes and everyone around them to an explosion that's designed to blind and deafen, with the potential to cause severe burns and permanent hearing loss—all before anyone has been charged with a crime. That doesn't seem like a close call.

Radley Balko is a senior editor at Reason magazine.