A federal appeals court on Monday issued one of the most comprehensive rulings yet limiting police use of Tasers against low-level offenders who seem to pose little threat and may be mentally ill.

In a case out of San Diego County, the 9th U.S. Circuit Court of Appeals criticized an officer who, without warning, shot an emotionally troubled man with a Taser when he was unarmed, yards away, and neither fleeing nor advancing on the officer.

Sold as a nonlethal alternative to guns, Tasers deliver an electrical jolt meant to subdue a subject. The stun guns have become a common and increasingly controversial tool used by law enforcement.

There have been at least nine Taser-related fatalities in the Sacramento region, including the death earlier this month of Paul Martinez Jr., an inmate shot with a stun gun while allegedly resisting officers at the Roseville jail.

As lawsuits have proliferated against police and Taser International, which manufactures the weaons, the nation's appellate courts have been trying to define what constitutes appropriate Taser use.

The San Diego County case is the latest ruling to address the issue.

The court recounted the facts of the case:

In the summer of 2005, Carl Bryan, 21, was pulled over for a seat-belt violation and did not follow an officer's order to stay in the car.

Earlier, he had received a speeding ticket and had taken off his T-shirt to wipe away tears. He was wearing only the underwear he'd slept in because a woman had taken his keys, the court said without further explanation.

During his second traffic stop in Coronado, he got out of the car. He was "agitated … yelling gibberish and hitting his thighs, clad only in his boxer shorts and tennis shoes" but did not threaten the officer verbally or physically, the judges wrote.

That's when Coronado Police Officer Brian McPherson, who was standing about 20 feet away watching Bryan's "bizarre tantrum," fired his Taser, the court said.

Without a word of warning, he hit Bryan in the arm with two metal darts, delivering a 1,200-volt jolt.

Temporarily paralyzed and in intense pain, Bryan fell face-first on the pavement. The fall shattered four of his front teeth and left him with facial abrasions and swelling. Later, a doctor had to use a scalpel to remove one of the darts.

Bryan sued McPherson, the Coronado Police Department and the city of Coronado, alleging excessive force in violation of his Fourth Amendment rights.

The officer moved to have the claim dismissed, but a federal trial judge ruled in Bryan's favor.

A three-judge panel of the 9th Circuit affirmed the trial judge's ruling on Monday, concluding that the level of force used by the officer was excessive.

McPherson could have waited for backup or tried to talk the man down, the judges said. If Bryan was mentally ill, as the officer contended, then there was even more reason to use "less intrusive means," the judges said.

"Officer McPherson's desire to quickly and decisively end an unusual and tense situation is understandable," Judge Kim McLane Wardlaw wrote for the court. "His chosen method for doing so violated Bryan's constitutional right to be free from excessive force."

Some lawyers called it a landmark decision.

Eugene Iredale, a San Diego lawyer who argued the case, said it was one of the clearest and most complete statements yet from an appellate court about the limits of Taser use.

He said after Monday's decision that courts will consider all circumstances, including whether someone poses a threat, has committed a serious crime or is mentally troubled.

"In an era where everybody understands 'don't tase me, bro,' courts are going to look more closely at the use of Tasers, and they're going to try to deter the promiscuous oversue of that tool," he said.

That's especially true in the context of those who appear to be emotionally disturbed or mentally ill, said Johnny Griffin III, a Sacramento plaintiffs lawyer.

Griffin represented the family of a troubled Woodland man who died under police restraint after being struck multiple times with Tasers.

In May 2008, Ricardo Abrahams walked away from a voluntary care facility and disobeyed the orders of officers called to check on his well-being. They shot him repeatedly with stun guns.

The case against the city of Woodland and its officers was settled in June for $300,000.

"I think it confirms what I and other lawyers in this area have been saying: You can't treat a person with mental illness the same as someone without mental illness," Griffin said.

Law enforcement authorities in Sacramento said they don't expect Monday's ruling to prompt much change.

Sacramento Police Department and Sacramento County Sheriff's Department policies permit the use of force to gain control of a suspect or prevent harm to others.

"Certainly the officer should be able to articulate the reason the force (was used), and a mere resistance to comply may not be enough," said Sheriff John McGinness.

Sgt. Norm Leong, spokesman for the Police Department, said his agency's policy on the use of stun guns mainly covers safety considerations. It doesn't list behaviors or situations that warrant using the devices, he said.

"Ideally, in every circumstance, we try to gain compliance verbally, and force is the last option we ever want to use," he said.