A man was driving a truck and was pulled over by the police. The police conducted a search of the vehicle and found drugs in a bag in the back of the truck. The bag belonged to the driver, but the bag was loaded into the truck by the passenger. The police were watching when the bag was placed into the truck, so that's not in dispute. The passenger claims that he did not know that the drugs were in the bag. How can the driver prove that the passenger is lying and that the drugs were placed in the bag by the passenger, without his knowledge?

