A Ramsey County judge on Tuesday removed a defense attorney from a murder trial that was to start this week, saying he has a potential conflict of interest involving a co-defendant who was to be a star witness for the prosecution.

Judge Rosanne Nathanson granted prosecutors’ request to remove private attorney Ira Whitlock from the trial for Durron Lashawn Brown of Minneapolis, who is accused of killing Marcelis L. Stafford, 21, on June 2 during a marijuana deal on St. Paul’s East Side. Brown has been indicted on charges of first- and second-degree murder.

Prosecutors alleged that Minnesota attorneys’ rules of conduct preclude Whitlock from representing Brown because Whitlock once represented co-defendant Fredericko Mobley. Prosecutors also alleged the lawyer provided Mobley with advice about the current murder trial, a claim that Whitlock says was fabricated.

Mobley had driven Brown and himself to and from the shooting scene, knowing that Brown was planning a robbery, court papers say.

On Feb. 22, Clayton Robinson, an assistant county attorney, filed the motion asking the judge to remove Whitlock from the case because Mobley revealed during an interview that Whitlock had represented him on several occasions. That should have been disclosed.

Robinson noted that Mobley’s credibility will be a key issue during the trial. Mobley had refused to sign a waiver that would have allowed Whitlock to proceed in the current case, Whitlock said.

On Tuesday, Nathanson halted the trial before jury selection began and set a hearing for March 13 to discuss the next steps.