Defense attorneys for an Illinois state representative facing bribery charges scored a victory Wednesday in their attacks against the credibility of the prosecutors’ main witness.

While State Rep. Derrick Smith was in Springfield for a House session, his attorney, Victor Henderson, was winning an argument in front of a federal judge in Chicago.

Judge Sharon Johnson Coleman ruled she would hold a rare hearing into whether law enforcement knowingly gave false information about a main witness in the Derrick Smith case.

Prosecutors say the source, whose name has not been made public, secretly recorded Smith in 27 conversations, including one in which the Chicago Democrat allegedly asked for a $7,000 cash bribe. Prosecutors say Smith is heard on tape saying he wants the money in cash because, he allegedly said, “I don’t want no trace of it.” In exchange for the money, prosecutors say Smith wrote a letter of recommendation for a grant application.

Early on in the case, federal investigators said the source who secretly recorded Smith had one prior arrest for domestic assault. Investigators also said the source had been paid $1,200 by the FBI for work in other investigations. 

But Smith’s defense attorneys call that witness a con man who has actually been arrested 20 times.

Prosecutors concur the source has been arrested for a range of offenses, including burglary, theft, drug offenses and weapons offenses. They say the witness has been convicted twice: once for a 2004 drug conviction and once in 1978 for burglary. The source was sentenced to probation for both offenses.

Smith’s attorneys also say the witness has not been paid $1,200 by the FBI, but $2,100.

The hearing scheduled for next month will look into what investigators knew about the witness, and that could impact the evidence allowed at trial.

Smith’s attorney would not comment after the judge’s decision on Wednesday.

Smith was first appointed to represent parts of Chicago’s West and North Sides in Springfield in 2011. His fellow House of Representatives members kicked him out of his seat last year after he was arrested. But Smith won back his House seat in November’s election, even though several high-ranking Illinois politicians supported his third party opponent.

Some of the same representatives who voted to kick Smith out of the House have said he will have a hard time representing his district with the criminal charges hanging over his head. They have said Illinois’ constitution forbids legislators from being kicked out of the House twice for the same offense.

Smith’s trial is scheduled to start in October.