LAFAYETTE — The former secretary and office administrator for 15th Judicial District Attorney Mike Harson pleaded guilty Monday to allegations of accepting at least $55,000 in bribes to give criminal defendants a break, mainly in DWI cases.

Barna D. Haynes, 58, of Lafayette, faces up to five years in prison on a count of conspiracy in an ongoing federal investigation of bribery in the local court system.

U.S. Attorney Stephanie Finley said Monday that she anticipates more guilty pleas in the investigation.

“We want the public to have faith that no one is allowed to buy themselves out of criminal activity in the Western District of Louisiana,” Finley said, referring to the federal court district that includes Lafayette.

Prosecutors allege the scheme lasted about four years, from March 2008 until Feb. 27, 2012 — the day FBI agents searched the local district attorney’s office.

Haynes, Harson’s former longtime assistant, was placed on leave about two weeks after the search and resigned in August.

The scheme was carried out without Harson’s knowledge or approval but occurred because of a “lack of oversight and safeguards,” according to a summary of the allegations filed by prosecutors.

Harson said in an email on Monday that he did not plan to comment on the case until Tuesday because he wants to review all the information related to Haynes’ plea.

Harson did say his office has no plans at this time to revisit any of the state court plea deals Haynes had arranged, in part because “I don’t know precisely which cases made the basis of the government’s case.”

Prosecutors allege a person identified in court documents only as “co-conspirator No. 1” paid Haynes $500 per case to obtain favorable treatment from the District Attorney’s Office.

The co-conspirator solicited “hundreds of thousands of dollars from individuals with criminal charges” on promises of getting them favorable treatment in court, according to court filings from prosecutors.

Many of the DWI defendants were allowed to participate in a special program under which criminal charges were quickly dismissed if they successfully completed certain probation requirements, such as drivers safety classes, substance abuse treatment and community service, according to prosecutors.

Prosecutors said those deals were formalized during special court sessions that Haynes coordinated and that all the cases were handled by the same assistant district attorney, though that person was not identified.

Prosecutors also wrote in court filings that a number of those special sessions were not held in open court but rather in a judge’s chambers.

No specific judge was identified as being involved.

Finley declined comment on whether “co-conspirator No. 1” is cooperating in the investigation or on how many other people have been targeted.

Haynes has agreed to cooperate in the case and has been given immunity for any future statements she gives to investigators, according to her plea agreement.

Haynes’ attorney, Frank Dawkins, declined comment on the guilty plea Monday.

“It speaks for itself,” he said.

Haynes admitted receiving about $55,000 in bribes, but prosecutors contend the amount exceeded $70,000, according to court filings outlining the terms of the plea.

“That may be something that is contested at sentencing,” Finley said.