Prosecutors in the Colorado theater shooting case are objecting to a defense request for a separate investigation into who told a reporter about a notebook defendant James Holmes sent to his psychiatrist.
In a filing Wednesday, the district attorney's office questioned whether the judge had the authority to appoint a special prosecutor for an inquiry into the sources.
Defense lawyers say the reporter's sources violated a gag order and then lied about it under oath.
The DA also objected to a defense request that the judge impose sanctions on the prosecution if the sources can't be identified.
Defense attempts to force the reporter to reveal her sources failed.
Holmes pleaded not guilty by reason of insanity to charges of killing 12 people and injuring 70 in the July 2012 attack.