The private investigator accused of securing special plea deals by handing out gifts and cash at the 15th Judicial District Attorney’s Office wants to block federal prosecutors from using a statement he gave to agents during a 2012 search of his home.

Robert Williamson faces trial June 8 on charges of fraud, bribery and lying to a federal agent in a wide-ranging investigation that already has netted guilty pleas from five others, including three former employees of the District Attorney’s Office.

Williamson was in court Thursday arguing that statements he gave while a team of federal and local agents were scouring his home for evidence on the evening of Feb. 27, 2012, should be thrown out because investigators never advised him of his right to remain silent or to contact an attorney.

Federal prosecutors argue 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 statement in court.

U.S. Magistrate Judge Patrick Hanna said he plans to rule on the issue by next week.

Williamson is accused of charging cash fees to his clients and using some of that money to bribe employees of the District Attorney’s Office to secure DWI plea deals allowing for a speedy disposition and for the charges to be wiped from the public record.

The February 2012 search of Williamson’s home came the same day the FBI also searched the District Attorney’s Office in Lafayette.

According to testimony at Thursday’s hearing, the FBI already had obtained court approval to tap Williamson’s phone and had been listening in on his conversations since September 2011.

Investigators kept the wiretap in place after the search.

Several of the recordings were played during the court hearing, including one about eight hours before the search that captured a conversation between Williamson and former District Attorney Mike Harson’s longtime secretary, Barna D. Haynes.

The two are heard discussing a defendant’s criminal history and her eligibility for the special plea program.

Haynes, a central figure in the case, already has pleaded guilty to a federal conspiracy charge and admitted accepting a total of $55,000 to arrange special plea agreements for DWI defendants at Williamson’s request.

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

Another recording played at Thursday’s hearing was of a call Williamson placed after the search to a local defense attorney.

Williamson told the attorney that agents asked him whether he gave money to Harson, and Williamson replied he’d given him only campaign contributions.

Harson has not been implicated in the bribery investigation, but it is thought to have been one of the major issues that led to his defeat at the polls Nov. 4 by retired prosecutor Keith Stutes.

A little more than an hour after the first call to the defense attorney, Williamson calls the man again and asks him whether the FBI should have read him a Miranda warning to advise him of his rights.

The attorney said that if the agents weren’t arresting him, then no, and that Williamson would be OK as long as he told the truth.

“You can’t not tell the truth to a federal agent,” he told Williamson.

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

Follow Lanie Lee Cook and Richard Burgess on Twitter, @lanieleecook and @rbb100.