The Louisiana Attorney General’s Office on Friday confirmed it is conducting a separate state investigation of a bribery scandal in the local court system that has already been under federal scrutiny for two years.

“I can’t say specifically what it is we are looking at, but I can tell you it is a serious and substantial look and investigation,” said Assistant Attorney General David Caldwell, who heads the agency’s public corruption division.

Caldwell also confirmed 15th Judicial District Judge Edward Rubin, who signed off on many of the DWI plea deals at the center of the scandal, is a potential witness.

Five people, including three former employees of the 15th Judicial District Attorney’s Office, have already pleaded guilty in the federal probe.

The Lafayette private investigator who allegedly orchestrated the scheme, Robert Williamson, is set to go on trial in federal court on Dec. 8.

The state Attorney General’s Office had announced last year that it would not pursue state criminal charges in the case, instead deferring action to federal prosecutors.

But federal authorities reached out to the AG’s office about a month ago and asked for an investigation into possible violations of state law, Caldwell said.

“Based on a conversation with them, our role has recently shifted,” he said.

Caldwell said the AG’s office did not intend to make the investigation public.

Its existence came to light during a court hearing in an unrelated case in Lafayette Parish on Thursday when Caldwell sought to recuse Rubin based on potential problems with him ruling on a case the AG’s Office is handling while the judge is also a potential witness in the bribery investigation.

Caldwell did not elaborate on why Rubin might be questioned but said the request for Rubin’s recusal “was just to avoid the appearance of impropriety.”

“I’m not saying he did anything wrong,” Caldwell said.

He said a hearing on the recusal motion might be set for next week.

Federal prosecutors allege that in return for gifts and cash, employees of the District Attorney’s Office allowed defendants to have their criminal charges quickly swept through the system if they successfully completed certain probation requirements, such as driver’s safety classes, substance abuse treatment and community service.

All the pleas required the OK of a judge, and Rubin signed off on many of them.

Rubin has not been named in the federal investigation.

The details of the plea agreements themselves have not been questioned in the federal probe, only that bribes were paid to allow defendants access to those special deals.

Although Caldwell declined to elaborate on details of the AG’s investigation, there are several potential state law violations in the case.

Defendants who allegedly gave Williamson money used for the bribes could be potential targets.

None of the DWI defendants has been charged so far, and it is not clear if they knew the money was for bribes or instead believed they were paying a fee for legitimate legal assistance.

State prosecutors also could pursue criminal charges related to falsified documents filed as evidence indicating that defendants had performed community service or met other requirements for the special plea deals when they had not actually done so.

The bribery scandal was a key issue in a heated 15th Judicial District attorney’s race that was decided Nov. 4, when retired prosecutor Keith Stutes ousted Mike Harson, who had served for 20 years.

Harson has not been identified as the target of a federal investigation, but federal prosecutors wrote in court filings that the scheme was carried out without the DA’s knowledge because of a “lack of oversight and safeguards.”