A former Gwinnett County police narcotics investigator pleaded guilty Friday to violating his oath of office and misdemeanor theft, bringing to a close a tumultuous chapter in the history of the department.

Vennie Rodrick Harden and his co-defendant, former Special Investigations Section supervisor Lt. David Butler, were indicted in 2010 for misusing money earmarked for undercover investigations. Harden was accused of forging Butler's name to authorize payments to a confidential informant.

Butler already pleaded guilty in March. As part of Harden's negotiated plea Friday, prosecutors agreed to drop three felony charges of forgery against Harden and reduce a felony theft charge to a misdemeanor.

Superior Court Judge Ronnie K. Batchelor sentenced Harden to five years of probation, with the first six months under house arrest. Batchelor also granted Harden first offender status, which means Harden's record will be cleared after he completes his sentence.

Gwinnett County District Attorney Danny Porter, who makes the final decisions about negotiated pleas, did not return a reporter's calls on Friday. Assistant District Attorney John Warr said that Harden was allowed to plead guilty to fewer charges because there were problems with the credibility of the main witness — a confidential informant who has a criminal record and is slated to be deported.

"He was telling us one thing, and the defense attorney another," Warr said.

Warr said the conflicting information might have damaged the informant's credibility before a jury if the case had gone to trial.

Harden's defense lawyer, Brian Steel, could not be reached for comment Friday.

Both Harden and Butler were arrested in October 2009, and the allegations — especially those against Butler — rattled the department.

Butler was a high-ranking supervisor and 24-year veteran of the department. He was accused of taking $4,000 in "flash money" from a safe in the Special Investigations Section. Flash money is used by undercover detectives to reassure drug dealers they are able to buy narcotics during an investigation.

The theft was discovered when another employee complained to internal affairs.

Indictments also show Butler used a county credit card to pay for food at Golden Corral and McDonald's, motel rooms and items at Starship Enterprise, an adult novelty store.

Butler, who resigned in 2009, pleaded guilty March 19 to charges of theft by taking, financial transaction card fraud and violation of oath of public office. He was sentenced to one year under house arrest and five years on probation. He also was ordered to pay restitution of $1,041 to the Gwinnett County Board of Commissioners.

Like Harden, Butler was granted first offender status. The officers' police certification has been yanked due to the convictions, so they cannot get another job as a law enforcement officer.