At the end of the movie, Marty is in the drivers seat of the dolorean, as the Doc puts the crystal logs in the fire to make the train move faster. He is in the driver seat for a couple of minutes. Then as the Doc is about to jump onto the dolorean from the front of the train, Marty opens the door from the passenger side, and is sitting in that seat. (remember there is a consul between the two seats.) Later in the movie as the dolorean is about to go off the cliff, he closes the door and next shot he is putting his hat on while he is seated in the DRIVERS seat. That right there defies something.