State Sen. Mark Leno

State Sen. Mark Leno (D-San Francisco) and other lawmakers plan to introduce legislation that would require smartphones and tablets to have "kill switches." Above, Leno in 2013. (Rich Pedroncelli, Associated Press / March 7, 2013)

SACRAMENTO — Citing skyrocketing thefts of smartphones and tablets, officials proposed Thursday that California become the first state to require the devices to be sold with "kill switches" that render them inoperable when stolen.

State Sen. Mark Leno (D-San Francisco) and other lawmakers said they plan to introduce such legislation with the support of Los Angeles Mayor Eric Garcetti and Police Chief Charlie Beck. L.A. had a 12% increase in mobile-device thefts in 2012, the most recent figures available.

The theft of such devices now accounts for nearly one-third of robberies in the United States, according to the Federal Communications Commission.

"This legislation is critical to reducing robberies," Garcetti wrote to legislators this week.

San Francisco Dist. Atty. George Gascon said more than half the robberies in his city involve theft of mobile devices. He said the industry has debated the use of deterrent technology for too long. "The wireless industry must take action to end the victimization of its customers," he said in a statement.

Some tech companies have started offering theft-deterrent technology. Apple's latest operating system includes a lockout feature. A LoJack app is installed in Samsung's Android phones that can make them useless, but a payment must be made to activate it.

Leno said he would propose that all new smartphones and tablets sold in California starting Jan. 1, 2015, have a kill switch or other protective feature. Such features come in multiple forms, including one that customers ask their phone companies to trigger. Another requires anyone who wants to re-register the phone to provide the original user name and password.

A kill switch would eliminate the value of stolen devices on the black market, according to Leno.

Supporters of the proposal say California's large market for mobile devices would make kill switches a nationwide standard. In 2012, about 1.6 million Americans had their smartphones stolen, according to Consumer Reports.

Industry officials say they are already starting to offer safety measures, and they are wary of government involvement.

"In general, we agree that it's smart to try to engage technology to improve public safety," said John Doherty, a vice president of the industry group TechNet, whose members include many firms that would be affected by a new regulation.

"But we are going to be very cautious about attempts to legislatively mandate future technology in products," Doherty added. "That impacts consumer price. That impacts innovation. And there are always unintended consequences."

Others expressed a wait-and-see attitude.

"It's premature for us to comment on any potential state legislation that's not yet been introduced," AT&T spokesman Lane Kasselman said.

Some industry critics have questioned manufacturers' interest in theft deterrents because victims typically buy new devices, increasing sales.

Megan Boken of Illinois was killed in 2012 when an armed man tried to steal her iPhone. Her father, Paul, has become an activist on the issue and supports Leno's idea.

"The theft of a smartphone ended my daughter's life and forever changed mine," Boken said. The upcoming legislation would "shut down the market for stolen smartphones, which will end the victimization of other innocent smartphone users and save lives."

patrick.mcgreevy@latimes.com