Felon Gun Possession Defense

Driver, who is a felon, in Washington State uses someone’s car and gets pulled over. As Officer approaches the passenger side window he asks if there is a gun in the car, driver confused says “no?” And the officer points to the passenger seat and says “well there’s a magazine right here” and points to a magazine that was out of the drivers view. He asks for his license, which driver produces, and if he can search the car. Driver responds with “no because I just got this car and I don’t know what’s in it and I don’t want to get in trouble” so officer asks him to step out of vehicle and says “alright well you are free to go but I’m impounding the vehicle and getting a search warrant”, officer lets him leave with no tickets, charges or warnings. driver later finds out there was an unloaded not stolen gun under the passenger seat that the magazine belonged to that the owner claimed to police. Driver did not know the gun was in the car when he drove it. Can he get charged with anything?