By law, Alexander Hernandez should have surrendered his gun to the state of California three years ago after a judge issued a restraining order against him for alleged domestic violence.
So one night recently , when the 26-year-old was at home in Whittier with his toddler, eight armed agents from the California Department of Justice banged on his door and took it from him.
Agents found the loaded .45-caliber handgun in a safe by his bed. Hernandez, who told the agents he had forgotten that he was supposed to turn in the weapon, was arrested on suspicion of illegally possessing a handgun, records show.
After assuring that the child had a baby-sitter, the agents drove off into the night in search of more illegal guns. Their quest took them across the San Gabriel Valley, from a retirement home to a gated community to a small house with rosebushes in front. In the living room of that house, a mother wept as agents arrested her son. A conviction for misdemeanor battery made it illegal for him to continue possessing his four guns.
California has the nation's only program to confiscate guns from people who bought them legally but later became disqualified. During twice-weekly sweeps over the last five years, agents have collected more than 10,000 guns.
But there are still more than 19,700 people on the state's Armed Prohibited Persons database. Collectively, they own about 39,000 guns. About 3,000 people are added to the list each year.
Clearing the backlog would cost $40 million to $50 million, according to Atty. Gen. Kamala Harris. She estimated that once the backlog is cleared, fielding teams large enough to keep up with people added to the list would cost about $14 million a year.
"This is about prevention," Harris said. "This is about taking guns out of the hands of people who are prohibited from owning them, and are known to be potentially some of the most dangerous people walking around.... It's just common sense."
As gun control has moved to the forefront of national debate, California's program is being studied as a potential model.
The list of prohibited owners is compiled by analysts who track gun sales back to 1996 and match them against databases listing criminal convictions, restraining orders and mental health detentions.
Sometimes the guns are used in killings before the state can retrieve them, according to state Sen. Mark Leno (D-San Francisco), who last month introduced legislation that would provide funding for more agents to conduct sweeps.
For example, Roy Perez had been on the list for three years before he shot and killed his mother, his neighbor and his neighbor's 4-year-old in Baldwin Park in 2008, officials said.
Until recently, the gun apprehension teams had received little attention in the five years they have been sweeping through neighborhoods. But they suddenly have become a topic of intense interest -- so much so that when agents rolled through Southern California earlier this month , their big, unmarked trucks were joined by two agents in a rented minivan large enough to carry journalists and camera crews.
The job requires a mixture of force and finesse. The agents show up in heavily armed teams, wearing black jumpsuits bulked up by bulletproof vests. But they don't have warrants and, unless their subject is on probation, they need permission to enter homes to search for guns. Obtaining a search warrant typically requires a reasonable suspicion that the gun would be on the premises, a difficult standard to meet based solely on information from a database, officials said.
Instead, they must talk their way in and coax gun owners into turning over their weapons.
Often, they come away empty-handed.
As the sun was setting, they arrived at the home of a man who had a domestic violence restraining order and was living in a Whittier neighborhood of small ranch homes and backyard stables. As agents walked to the door, neighbors came by on horseback, staring.
The man told the agents he didn't have the gun anymore; it was at his brother's house.