The stand-your-ground doctrine, which has vaulted into national prominence with the killing of Florida teenager Trayvon Martin, isn't limited to the two dozen states that have passed laws since 2005 expanding the right to use deadly force in confrontations.

It's also the rule in California, by court decree. For more than a century, the state's judges have declared that a person who reasonably believes he or she faces serious injury or death from an assailant does not have to back off - inside or outside the home - and instead can use whatever force is needed to eliminate the danger.

The California Legislature has never enacted one of the National Rifle Association-sponsored laws, pioneered by Florida in 2005, that spell out the rights of a defendant in such confrontations and the procedures for applying them in court. But in California, the judicial rulings had much the same effect. The rulings are binding on state courts and are reflected in judges' instructions to juries in cases involving claims of self-defense.

The instructions say a person under attack is even entitled, "if reasonably necessary, to pursue an assailant until the danger of death or great bodily injury has passed. This is so even if safety could have been achieved by retreating."

Most states had similar rules until 30 or 40 years ago, when some passed laws barring a claim of self-defense outside the home if the person could have fled safely, said Andrea Roth, a UC Berkeley law professor. She said almost all states still allow the use of deadly force against home intruders.

"California's law perpetuates the old frontier rule," she said. "This is not some new brainchild of the NRA."

The Florida law, however, contains a major pro-defense feature absent in California and other states: a pretrial, nonjury hearing in which a judge, after considering the evidence, decides whether it's more likely than not that the defendant acted in self-defense.

If so, the judge must dismiss the charges. In California, such factual disputes must be resolved by a jury.

In the Martin case, a judge will have to decide whether it was more likely than not that George Zimmerman, the neighborhood watchman who fatally shot the unarmed 17-year-old in a gated community in Sanford, Fla., on Feb. 26, reasonably believed he was in danger from Martin.

"That hearing is the big difference," said Marty Vranicar, assistant chief executive of the California District Attorneys Association and a former Los Angeles prosecutor. "A jury's going to be deciding that in California. ... I have often had more luck presenting my case to 12 fact-finders than to an individual bench officer."

There are also differences in the legal culture of California and a state such as Florida, where self-defense rights have been broadened by the Legislature, said Robert Weisberg, a Stanford law professor.

Passage of such a law is "a signal to the courts that the overall legislative intent is to be extremely deferential to defendants who claim self-defense," he said.

The laws also have a different practical impact, said Adam Winkler, a UCLA law professor, because it's easy for Floridians, including Zimmerman, to get a permit to carry a handgun, but much more difficult in California. That disparity may affect the number of stand-your-ground homicides in states with permissive gun laws, he wrote in a recent article, although studies are conflicting.

But even Californians who illegally carry handguns can invoke the stand-your-ground doctrine, as shown in a 2005 ruling by a state appeals court in Santa Ana. The court overturned the attempted-manslaughter conviction of Lenard Rhodes, who shot and wounded a man who he said had approached his car with a gun.

Although Rhodes could have driven off - and although he was a convicted felon who had no right to possess a gun - the court said he "had the right to defend himself, stand his ground and use the amount of force reasonable under the circumstances." Because the jury was not given those instructions, the court said, Rhodes was entitled to a new trial.

Bob Egelko is a San Francisco Chronicle staff writer. begelko@sfchronicle.com

This article appeared on page C - 1 of the San Francisco Chronicle