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Twenty New Orleans police officers have been charged in a series of probes by the Justice Department's civil rights division since 2010. A retired sergeant who was assigned to investigate deadly police shootings on a bridge after Hurricane Katrina will be the last of those officers to get his day in court.

A trial is scheduled to start Monday for Gerard Dugue, who is charged with participating in a cover-up to make it appear police were justified in shooting six unarmed people, killing two, on the Danziger Bridge less than a week after the 2005 storm.

A judge ordered separate trials for Dugue and five other current or former officers who were convicted in August of civil rights violations stemming from the bridge shootings.

"He is completely and totally innocent," said Dugue's attorney, Claude Kelly. "He has said that from day one, and that will be proven in court."

The hurricane, which struck Louisiana and Mississippi on Aug. 29, 2005, drove a wall of water into the coast. Levees broke and flooded roughly 80 percent of New Orleans, plunging the city into chaos and subjecting police to harsh, dangerous conditions.

The storm also cast a spotlight on a troubled police department that has been plagued by corruption for decades. In Katrina's aftermath, federal authorities launched a new push to clean up the police force. The criminal probes were only part of the effort. The Justice Department also embarked on a top-to-bottom review of the department that produced a scathing report on its practices.

Dugue isn't charged in the shooting. He wasn't on the bridge the morning of Sept. 4, 2005, when police shot and killed 17-year-old James Brissette and 40-year-old Ronald Madison, a mentally disabled man. Dugue didn't get involved in the case until several weeks later, when the department assigned him to help another sergeant investigate.

A jury convicted retired Sgt. Arthur Kaufman of participating in a cover-up that included a planted gun, phony witnesses and falsified reports.

Unlike Dugue, Kaufman was on the bridge in the aftermath of the shootings. Former Lt. Michael Lohman, who was the ranking officer on the scene, initially assigned Kaufman to lead the investigation.

Kaufman told the FBI he found a revolver in a grassy area beside the bridge a day after the shootings. Prosecutors, however, said Kaufman retrieved the gun from his home several weeks later and turned it in as evidence, claiming it was thrown off the bridge by Ronald Madison's brother Lance.

Kaufman and Dugue interviewed officers who fired their guns on the bridge. They allegedly co-authored a report that included statements they knew to be false. An indictment claims the two investigators told the officers to "make sure they had their stories straight" before they gave taped statements.

Kaufman's attorney, Stephen London, argued during last year's trial that Dugue was responsible for the contents of the department's official report on the shootings.

Dugue allegedly lied to a federal agent when he said he didn't question the truthfulness of the officers' statements or doubt their actions were justified.

"In fact," the indictment says, "he had many 'red flags' and 'question marks' about the officers' stories, but he reported the questionable information as fact and relied upon it without qualification."

Dugue received a separate trial after prosecutors argued that statements he made during his FBI interview could incriminate the other defendants.

The jury in last year's trial heard five weeks of testimony by roughly 60 witnesses. Dugue's trial is expected to last two to three weeks.

Five other former officers pleaded guilty to participating in a cover-up of the bridge shootings and are serving prison terms.

Dugue's trial may not be the last for an officer charged in the Justice Department probes. A judge ordered a new trial for former Lt. Travis McCabe, who was convicted in December 2010 of helping cover up the fatal shooting of 31-year-old Henry Glover after Katrina.

U.S. District Judge Lance Africk ruled McCabe deserves a second trial because newly discovered evidence — a different copy of the report that McCabe is accused of doctoring — surfaced after his convictions. Prosecutors are appealing that decision.

Jurors also convicted a former officer, David Warren, of fatally shooting Glover outside a strip mall and convicted another officer, Gregory McRae, of burning Glover's body in a car. Two others were acquitted in the case.

Two other investigations resulted in charges against officers: In April 2011, a jury convicted two officers of charges stemming from the fatal beating of a 48-year-old handyman in July 2005. And in December 2011, a jury convicted one officer and acquitted another of lying about a deadly shooting outside the city's convention center after Katrina.