By BRIAN MELLEY, Associated Press

LOS ANGELES (AP) — Former Los Angeles Sheriff Lee Baca was indicted Friday on charges of obstructing justice and conspiring with underlings to derail a federal investigation into corruption and beatings in the nation's largest jail system.

The charges that carry up to 20 years in prison come just days after Baca withdrew a guilty plea to lying to investigators and said he would go to trial to "set the record straight" before he is incapacitated by Alzheimer's disease.

Baca, 74, made the decision knowing federal prosecutors were likely to bring stiffer charges, but his lawyers said he didn't have much choice when negotiations collapsed after a federal judge rejected a plea deal as too lenient. That agreement called for no more than six months behind bars.

Defense lawyer Michael Zweiback said it appeared the judge was seeking several years in prison, and Baca needed certainty because his condition has already started to deteriorate.

"We have a very, very small window of time that we believe Mr. Baca's life will be normal," he said Monday. "If there was a possibility that he was going to go beyond his good years in prison, then he should go out and fight."

Baca is now facing the original charge of lying to federal authorities and new charges of obstruction of justice and conspiracy to obstruct justice.

Defense lawyers had anticipated the stiffer charges, and said Friday that they represent punishment for Baca's decision to go to trial.

Attorney Nathan Hochman said prosecutors revealed in court filings that evidence is very thin to support the obstruction case against Baca.

"If you look in the government's own sentencing position on this case, they go through each one of the different actions of alleged obstruction, and you'll see, highlighted at the end of each paragraph, they'll say: 'Baca was not involved. Baca did not participate,'" Hochman said.

Twenty members of the Sheriff's Department have been convicted in the probe that began after deputies discovered an inmate was an FBI informant gathering evidence about civil rights abuses and corruption in the jails.

Baca had denied any involvement in a scheme to hide the informant from the FBI in what conspirators dubbed "Operation Pandora's Box." The inmate was moved to different jails and listed under fictitious names. Deputies intimidated an FBI agent with the threat of arrest at one point.

In the plea agreement that has since been withdrawn, Baca acknowledged for the first time that he had lied to investigators and was aware of efforts to thwart the investigation. Jurors will not be told that he previously pleaded guilty.

Baca abruptly stepped down in January 2014 after heading the nation's largest sheriff's force for 16 years.

His second in command, Paul Tanaka, who unsuccessfully campaigned to replace Baca, was convicted and sentenced to five years for his role in the conspiracy.

The president of the union representing sheriff's deputies, which criticized the plea deal as a slap on the wrist while rank-and-file officers got stiffer terms, said Baca's punishment should be at least as harsh as Tanaka's.

"Baca knew what was going on, and he perpetuated and encouraged the culture," said George Hofstetter, president of the Association for Los Angeles Deputy Sheriffs. "When confronted with the mess he had created, Baca blamed his subordinates instead of taking responsibility as a leader should."