A grand jury in rural Louisiana considers Tuesday whether to bring murder charges against a Taser-wielding police officer in what may become a seminal case in the hotly debated history of stun guns.

No US jury has ever convicted a police officer in connection with a death related to use of an electroshock weapon. But the number of deaths in which the guns have played a role has been growing, along with their use in law enforcement agencies.

Now, the coroner in Winnfield, La., has found the death of one Baron "Scooter" Pikes to be homicide by Taser, intensifying a simmering controversy over the devices and exposing the tense tug of war between police and young black men in rural Louisiana.

After Winnfield Parish police took Mr. Pikes, who is black, into custody one January morning, a white police officer fired a Taser, jolting Pikes nine times in the span of 14 minutes. Pikes never woke up.

Police said the 21-year-old Pikes was on drugs and uncooperative, but coroner Randolph Williams took a different view. In a report last month, he said he found no signs of a physical struggle, of drugs, or of any medical condition that could have exacerbated the jolts' effect.

As police departments across the US look for nonlethal ways to subdue out-of-control people, a big question is whether such devices reduce violence or, in effect, can increase the likelihood of violence, even torture. The Pikes death is just one case, but it appears to show that the combination of simmering racial tensions and insufficient police training can be lethal when injected with a 50,000-volt jolt.

"If the Taser was indeed the cause of death, this could be an interesting case," says Andrew Scott, former police chief of Boca Raton, Fla., who has testified on the behalf of officers in stun-gun cases. "Given the historical corruption of law enforcement in the area, and the fact that the young man was tased nine times, something is definitely wrong with this picture."

Two-thirds of all police departments in the US own at least one electroshock weapon. The guns have played a role in nearly 300 deaths in the US and Canada since their introduction in 1998, Amnesty International reported in June. Yet most wrongful-death lawsuits have gone the Taser's way, with juries finding that factors ranging from hard drugs in a person's system to existing medical conditions were responsible for or contributed to their deaths.

The weapons, also called electronic control devices, are part of a transformation in policing, away from bullets and guns and toward "Star Trek"-like devices that can, from a law-enforcement standpoint, safely and quickly defuse volatile situations.

"We didn't get this [negative] reaction when nightsticks were used to split heads open, but because of the technology and what it does, the media have really exacerbated the issue of the Taser," says Mr. Scott. "The upside of the Taser far outweighs the unfortunate abuse or downside."

But with some 260,000 units in the hands of law enforcement officials, and with no major federal regulation governing their use, stun-gun use in cases like the one in Louisiana is revealing unintended drawbacks of this particular tool of policing, says Thomas Luka, a defense attorney in Orlando, Fla. Used most often before officers are physically threatened, the devices are changing the relationship between police and the populace, especially on the streets.

"We're seeing injuries that wouldn't normally happen on a routine traffic stop, and all of a sudden they're happening," says Mr. Luka.

The American Civil Liberties Union has not called for a ban on devices such as Tasers. But in the light of studies that show potential health effects of getting jolted and a general lack of training, national standards, and federal oversight, the ACLU says the devices have created a troubling gray area for US civil rights.

"The Taser in many cases is going to be safe, but it's those other cases, which actually are prevalent in the population that police interact with, that we have a lot of concerns about," says Mark Schlosberg, an electroshock-weapons expert with the ACLU in San Francisco.

A federal National Institute of Justice study released in June drew this conclusion on devices such as Tasers: "Although exposure ... is not risk free, there is no conclusive medical evidence within the state of current medical research that indicates a high risk of serious injury or death from the direct effects of CED [conducted-energy device] exposure."

Still, the public shows signs of souring on the devices. Seven states have banned their use, and some police departments are reevaluating their stun-gun policies, specifically to wait for an imminent threat of physical violence before resorting to their use and to restrict officers to fewer than three jolts before moving on to hand-to-hand restraint. But for many police departments, critics say, electroshock weapons are routinely and increasingly deployed in a variety of situations, with plenty of room for questionable improvisation.

"Police sometimes do things they're not supposed to do, and if you put the temptation in front of them, if you tell 100 police officers that, 'Here's your Tasers, and you're not supposed to use them to punish,' someone is going to use them to punish. It's predictable," says Michael Baden, the former chief medical examiner for the New York State Police.

The Winnfield Parish case is likely to test all those aspects, highlighting racial tensions between blacks and police evident in many parts of the US. Roughly corresponding to overall crime data, 46 percent of the people who died in stun-gun-related incidents were black and 36 percent were white.

Winnfield Parish, birthplace of famed Louisiana Gov. Huey Long, has a long history of police corruption. The officer who administered the Taser to Pikes, Scott Nugent, was a rookie cop hired by a police chief who served time on a drug charge but was pardoned by former Gov. Edwin Edwards, who himself is now in federal prison.

A first cousin of Mychal Bell – the main defendant in the Jena 6 case that last year sparked the century's largest civil rights march – Pikes at the time of his arrest, on an outstanding warrant, struggled with police and then fell sick, complaining of asthma and the effects of PCP, police said after his death. But bystanders said Pikes, who knew the officers, pleaded with them, "Don't tase me again, please."

The Police Department has admitted no wrongdoing, though the City Council fired Nugent in May. The medical examiner is risking his relationship with the police department by listing the death as a homicide, but his autopsy was sound, according to Mr. Baden, who reviewed the findings.

"This is a major case," says Carol Powell-Lexing, a lawyer representing Pikes's family. "It's significant in the sense it shows how this young officer exceeded his authority and use of force, and it shows how dangerous those Tasers are. The community won't rest until they see appropriate relief in regards to this situation."