Ever since the San Francisco Sheriff's Department rejected Tom Boyer's application to carry a concealed weapon 10 years ago, the 55-year-old Mission District resident has felt vulnerable on city streets.

Standing 5 feet 3 and weighing 135 pounds, Boyer said he's been the victim of several late-night assaults, including one in the Castro in which he thinks the assailants attacked him because he's gay. He avoided a beating that time by using pepper spray, he said.

"It's not as if the next time it happens I'd instantly pull out a handgun," Boyer said. "But it has shown me the life-and-death potential was there. I've had some close calls, and a concealed handgun is like an insurance policy."

It's a policy Boyer and other California gun advocates hope a court will soon make easier for them to purchase.

In December, a panel of the Ninth U.S. Circuit Court of Appeals in San Francisco heard three cases that could lift local law enforcement agencies' discretion to grant or deny concealed-weapons permits.

County policies vary greatly

Policies now vary from county to county. Some make it relatively easy to obtain a permit, while in others - including San Francisco - it's all but impossible. The cases supported by Boyer and other would-be permit holders ask the courts to order an across-the-board standard in California.

That standard would be met if an applicant merely declared that he or she needed a concealed-weapon permit for self-defense. Both sides of the debate agree such a ruling would allow almost anyone besides "prohibited persons" - such as convicted felons and the mentally ill - to get a permit.

If that happens, gun advocates say, the number of permits in California will rise from an estimated 35,000 in 2012 to as many as 1.2 million within four years of the ruling.

"At its core, people should have the right to carry a concealed weapon for self-defense," said Brandon Combs, an attorney for the advocacy group Calguns Foundation, which filed the legal cases. "From Shasta County to San Diego, the minimum policy of issuing a license to those who are eligible should be the same."

As it stands, each city police chief and county sheriff is allowed to award permits at their discretion. San Francisco has long been stingy with the permits. The sheriff's office has awarded just one in the past 30 years - and it expired in 2008. Two residents have permits obtained through the Police Department, according to city records.

It's almost as hard to get a permit in Marin County, where just 35 people have one. Elsewhere, however, the authorities are much less strict.

A total of 165 people have concealed-weapons permits in Alameda County. In Solano County, 320 people can carry concealed weapons. In Kern County, the total is 3,547.

More shootings

Ben Van Houten, managing attorney of San Francisco's Law Center to Prevent Gun Violence, said the federal appeals court's ruling, expected within the next few weeks, could put more guns on the streets and lead to more shootings.

"A permissive concealed-weapons permitting system that allows people to carry loaded handguns without showing any specific need to carry just increases the likelihood that the normal, day-to-day conflicts people have will escalate into gun violence," Van Houten said.

There's little question that the demand for concealed weapons permits is high. After Wisconsin passed its first statewide law granting such permits in 2011, more than 44,000 people applied within four weeks. The state Justice Department granted 13,085 of the applications.

Combs, the Calguns attorney, said some California counties have long waiting lists of people hoping for permits.

Yearlong process

Most counties require an applicant to pass a background check, a shooting proficiency test and a psychological evaluation. The process can take a year. Applicants also have to submit a sworn affidavit explaining why they need to carry a concealed gun.

In San Francisco's Glen Park neighborhood, retiree Jeff Levinger said he would be among the first in line for a permit if the city's restrictions were loosened.

Levinger said he went to police headquarters last year after he was the victim of several street assaults but that no one knew how he could apply for a permit. Frustrated, he said, he finally gave up.

Levinger said that as a law-abiding citizen, he has the constitutional right to pack a hidden gun.

"It's my opinion, we don't need a reason," Levinger said. "Self-defense is a basic right, and that should be enough."

Justin Berton is a San Francisco Chronicle staff writer. E-mail: jberton@sfchronicle.com Twitter: @justinberton