A private investigator accused of helping set up a DWI bribery scheme in the 15th Judicial District Attorney’s Office has lost his fight to keep statements he gave to federal agents out of his trial.

U.S. District Judge Elizabeth Foote, in a decision made public Thursday, ruled that prosecutors can use Robert Williamson’s statements in his June 8 trial on charges of fraud, bribery and lying to a federal agent.

The investigation already has brought guilty pleas from three former employees of the District Attorney’s Office.

The scandal also was a central issue in a bitter election campaign last year that ended with retired prosecutor Keith Stutes ousting longtime District Attorney Mike Harson, who has not been implicated in the case but who was chastised by federal prosecutors for a “lack of oversight and safeguards” in his office.

Federal prosecutors allege Williamson charged hefty fees to his clients and then doled out cash and gifts to District Attorney’s Office employees to secure special plea deals — mainly in DWI cases — that allowed for a speedy resolution of the charges, which, in many cases, were wiped from the public record.

Prosecutors have not said how many plea deals he arranged or how much money changed hands over the four years the alleged scheme ran from 2008 to 2012.

But Harson’s longtime office administrator, Barna D. Haynes, admitted to accepting a total of $55,000 to arrange special plea agreements for Williamson.

Others in the District Attorney’s Office admitted to smaller cash payments and gifts that included bicycles, clothing and an autographed New Orleans Saints hat.

Haynes has agreed to testify against Williamson in a move that could affect her pending sentencing.

Evidence in the case also includes several recorded conversations obtained via a wiretap on Williamson’s phone, which federal agents monitored for several months.

The statements at issue in Foote’s court ruling this week were made by Williamson to agents during a search of his home on Feb. 7, 2012, the same day agents searched the District Attorney’s Office in Lafayette.

Williamson argued his statements should not be allowed as evidence because investigators never advised him of his right to remain silent or to contact an attorney, the so-called “Miranda warning.”

Prosecutors countered that Williamson was not under arrest or even being detained at the time, conditions that would require investigators to read him his rights if they planned to use his statements in court.

U.S. Magistrate Judge Patrick Hanna had sided with prosecutors last month in a recommendation to Foote that the statement be allowed as evidence.

While Williamson’s federal case moves forward, a separate state investigation continues into the bribery scandal.

The Louisiana Attorney General’s Office confirmed the investigation last year but has offered no details on what state authorities are scrutinizing.

Defendants who allegedly gave Williamson money used for the bribes could be potential targets, as well as any other officials involved in the scheme but not targeted by federal authorities.

Assistant Attorney General David Caldwell, who heads the agency’s public corruption division, said in an e mail Thursday that the case remains active.

“We expect some movement in the near future,” he said.