Criminals can be so stupid. If you're gonna break the law, at least be smart about it, i.e., don't do drugs or transport drugs in a car that has its windows tinted to the point where a police officer might want to check the legality of said windows.
The trooper asked Smith to roll down his driver's side window so that he could check the tint. That's when, according to the FHP, Smith opened the driver's door and the trooper smelled a strong odor of burned marijuana coming from inside the vehicle and observed marijuana residue on the driver's seat and on the center console.