All smartphones sold in California would have to come with a "kill switch" to render them inoperable if lost or stolen under a bill passed by the legislature on Monday, the latest effort to stem an epidemic of phone theft in the most populous U.S. state. The bill would be the strongest effort yet by a U.S. state to fight smartphone theft, which accounts for more than half of all crimes in several of the state’s large cities, including San Francisco and Oakland. "Our goal is to swiftly take the wind out of the sails of thieves who have made the theft of smartphones one of the most prevalent street crimes in California’s biggest cities," said Democratic Senator Mark Leno of San Francisco, the bill’s author.