In response to the massacre at Sandy Hook Elementary School in Connecticut five years ago, outraged California lawmakers launched a crackdown within months of the tragedy that has seized 18,000 firearms, including assault rifles, from thousands of people convicted of felonies, subject to domestic violence restraining orders or judged by the courts to be severely mentally ill.

The Armed and Prohibited Persons System identifies those who legally purchased guns but were later convicted of a felony or otherwise disqualified from holding firearms. However, the list of prohibited persons grew in its early years — faster than the understaffed state Department of Justice could seize guns in door-to-door searches.

The accuracy of the database is of concern to Craig DeLuz, a spokesman for the Firearms Policy Coalition, a group advocating for gun owners. When a temporary restraining order is lifted, a gun owner recovers the right to have guns, he said, adding that the change is not always recorded in a timely manner.

“When the information is inaccurate, you potentially put people at risk because you have the Attorney General’s Office sending armed SWAT teams to people’s homes to confiscate firearms,” DeLuz said.