guilty of possesion?

My boyfriend was driving a car not registered to him. He was pulled over and because he didn't have a drivers license
the car was searched. He had none of his belongings in the vehicle. On the floorboard with some trash was an empty
cigerette pack with substance inside. He was arrested. Following arrest police checked residence and found no evidence of substance abuse but did find that his brand of cigerettes different from substance package. Is he still guilty of possesion?

Yes, unless he hires a good attorney to plead his case and the court agrees.