LOS ANGELES (AP) — Overworked supervisors missed signs that should have tipped them to corruption in a local police station, Los Angeles Police Chief Bernard C. Parks says.

Moreover, at least four officers linked to the scandal never should have been hired because they had been arrested or had outstanding debts, Parks said.

"There's generally a lack of oversight by command supervision going all the way up through the department," Parks said Wednesday, outlining the department's widening investigation of the scandal to the City Council.

Parks said "telltale signs" of poor performance, such as suspicious paperwork, were missed by supervisors — not only at the Rampart Division at the center of the investigation, but throughout the 10,000-member police force.

As a result of the investigation, more than 30 convictions have been overturned. Prosecutors planned to ask today that convictions of nine more defendants be voided because the cases were compromised by false or planted evidence, the district attorney'soffice said.

At least 20 officers have been relieved of duty, suspended or fired or have quit since the scandal broke last fall. Parks declined to provide a new count Wednesday.

The corruption came to light after former Officer Rafael Perez was convicted of stealing cocaine from a police evidence locker.

Perez, hoping for a more lenient sentence, said officers in the Rampart Division near downtown framed and brutalized people and even shot unarmed suspects. Lawsuits involving such claims could cost the city $125 million, according to one official estimate.

Parks said 99 defendants in 57 cases involving Perez may have been framed through perjury or false arrest.

The Los Angeles Times reported today that District Attorney Gil Garcetti is adding seven prosecutors to a task force of 10 lawyers in anticipation of years of work.

The number of cases eventually could rise to several hundred as the scandal moves beyond the Rampart station, the newspaper said, citing confidential sources.

Parks said at least four officers linked to the scandal never should have been hired because background checks showed they had previous arrests or financial problems.

"They were misdemeanor arrests, alcohol ... domestic violence, things like that," Parks said. "Those are the kinds of things that are red flags for us as it relates to how an officer will perform in the future."

Initially, the four were disqualified but were later hired, in some cases after civil service appeals, the chief said.

Parks said he did not know whether Perez was one of the four officers whose background checks turned up problems that should have kept them off the force. Parks did say that one of the four was fired in 1998 for allegedly beating a handcuffed suspect inside the Rampart station.

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