A federal judge in Chicago has put the brakes on attempts to investigate whether federal agents lied about a key witness in the case against an Illinois lawmaker.

Prosecutors allege they caught State Rep. Derrick Smith, a Chicago Democrat, on tape accepting a $7,000 bribe. Smith’s attorneys say FBI agents didn’t disclose the 20 prior arrests of the person who secretly recorded Smith. Victor Henderson, Smith’s attorney, has said he wants the 27 secret recordings thrown out before the trial. He’s argued in court filings that separating the source’s background from the tapes gathered against Smith is no easier than separating the yolk from an egg.

“It makes a big difference when you’re starting a case out whether you have a nun or a Sister Bertrille who’s at the center of it, or a confidential informant who’s got a criminal history that’s 40 pages long,” Henderson said leading up to the judge’s decision on Thursday.

But Judge Sharon Johnson Coleman ruled Thursday there’s enough evidence to continue the case against Smith, even if the source’s credibility is an issue.

“The source’s credibility plays no role in establishing that the words were spoken,” she wrote in her decision, referring to the alleged secret recordings of Smith.

Smith’s trial is scheduled to start in October.