CHICAGO (AP) — A judge in Chicago has scheduled a March 12 trial date for an Illinois state senator accused of trying to board a flight with a gun and ammunition, but a police officer's testimony about having trouble finding the small gun in a garment bag may help establish the politician had forgotten the gun was there.

During a hearing Thursday, Judge Ann O'Donnell found probable cause to continue the case against Donne Trotter. He faces a felony gun charge after being stopped by security last year at O'Hare International Airport.

Trotter's attorney, Thomas Durkin, said after the hearing that he'd hoped the judge would dismiss the case but said he believes prosecutors won't be able to prove that Trotter knew the gun was in the bag when he headed to the airport.

"We're very confident going forward. We'll just take it to the next step," Durkin said.

Trotter didn't speak to reporters.

Trotter, 62, had been considered a front-runner to replace former U.S. Rep. Jesse Jackson Jr. in Congress, but he withdrew from the 2nd Congressional District race last month, saying he didn't want the gun charge to detract from the district's important issues.

Trotter was arrested Dec. 5 when security screeners at O'Hare International Airport found an unloaded .25-caliber Beretta handgun in his bag. Trotter had planned to board a flight for Washington.

The Chicago Democrat told airport security he uses the handgun for his job with a security company and had forgotten it was in his bag, according to a police report.

Chicago Police Officer Vince Bielicki testified Thursday that airport security called him after an outline of a gun was seen in a screened bag. Bielicki told the judge he initially couldn't locate the weapon in the bag but eventually found it in an outer zipped pocket. Bielicki said Trotter cooperated with authorities at the airport.

After the hearing, Durkin told reporters the officer's testimony helps his client.

"The most telling fact was the police officer said when he went to look for it he couldn't even find it," Durkin said. "He didn't even find it the first time he looked for it."