A records search showed that it was reported stolen on April 10, according to the police report.
At the time of his arrest, Banks was weeks away from finishing parole in a 2011 aggravated unlawful use of a weapon case, in which he was caught in the 6400 block of South Eggleston Avenue on Oct. 9, 2011, with a gun that had had its serial numbers defaced.
Banks’ lawyer, Sam Adam Jr., filed a memorandum asking for a signature bond, stating that Banks is engaged, has one child and another that is due on Tuesday.  He said Banks has signed with a major record label but has yet to make a significant amount of money and therefore has little means to post bond.
Attached to the memorandum are handwritten statements from several alleged witnesses to the incident, all claiming that Banks did not own the gun.
One of the statements is from a 20-year-old man who claimed it was his gun, and that he told police he was the one who threw it in the car. The man, who is a convicted felon acquitted of attempted murder in March, claimed in his statement that “police did not want to listen to him."
Banks performs under the name Lil Durk. He is a friend and associate of South Side rapper Chief Keef, who also has been under public scrutiny since the September 2012 shooting death of aspiring rapper Joseph Coleman, 18, not far from his boyhood home in Englewood.
The slaying of Coleman – known as Lil Jojo – garnered national attention following reports that Chicago police were looking into whether a war of words in the hip-hop community between him and Chief Keef’s crew played a role in the slaying. Hours after Coleman’s death, a taunting tweet was sent on Chief Keef's account mocking Lil Jojo.
Law enforcement sources said Lil Durk is part of the same crew that had been at odds with Coleman, a feud that investigators have documented from YouTube videos and Twitter feeds.
The sources have also said the slaying might be tied to a conflict between the Brick Squad faction of the Gangster Disciples and the Lamron faction of the Black Disciples.
No one has been charged in Coleman's slaying.
In March, Chief Keef -- whose real name is Keith Cozart -- completed a 60-day stay in a juvenile prison for violating his probation on a gun conviction. Since then, he’s been arrested twice.
On May 20, he was arrested in the Atlanta area when police allegedly found him smoking marijuana in a hotel room. A week later, he was arrested on suspicion of speeding at 110 mph on the Edens Expressway in Chicago’s northern suburbs, police said.
Tribune reporter Liam Ford contributed
Twitter: @ChicagoBreaking