The state is the first to adopt such a policy, although several states permit searches for relatives, the Los Angeles Times reported. The state crime lab will alert police when scientists find partial DNA matches.

State Attorney General Jerry Brown said California must take steps to lock up violent criminals.

"We have 2,000 murders a year in California -- that is 10,000 since the Iraq war started -- and that is a lot of killing," Brown said. "When you see it and see the victims and have to go to funerals, it is pretty serious stuff."

In Britain, police have reported a success rate of 10 percent to 14 percent using partial DNA matches. In one case, they identified a suspected serial rapist because his sister had been arrested for drunken driving, and her DNA was in the database.

Civil libertarians are concerned about privacy, especially with California's plans to expand the database to include people who are arrested without being convicted.