Police need reasons to believe a suspect is dangerous before firing a TASER and can't use their stun gun simply because the person is disobeying orders or acting erratically, a federal appeals court in San Francisco ruled Monday.

The decision by the Ninth U.S. Circuit Court of Appeals sets judicial standards for police and for people who claim they were victims of excessive force after police hit them with a TASER dart.

"The objective facts must indicate that the suspect poses an immediate threat to the officer or a member of the public," Judge Kim Wardlaw said in the 3-0 ruling.

Though stun guns may offer a valuable, nonlethal alternative to deadly force in defusing dangerous situations, Wardlaw said, they inflict a "painful and frightening blow" and must be used only when substantial force is necessary and other options are unavailable.

"It's a significant use of force, not like cuffing someone or using pain compliance or pepper spray," said Eugene Iredale, a lawyer for a San Diego-area man who was Tasered by a police officer who had stopped him for not wearing a seat belt. "It's not to be used promiscuously or lightly."

The ruling allows Iredale's client Carl Bryan to go to trial in his damage suit against Brian McPherson, a policeman in Bryan's hometown of Coronado. McPherson's lawyers were unavailable for comment.

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