Sounds like there isn't any evidence that he was high at the time, since THC can stay in your system for awhile after you use it (depending on the user). So unless he had a hand in his gun, hand on the wheel, and a hand on a joint, and there is a picture of this, it sounds like a bunch of B.S. Especially since he only had 2 hands.
Also, I thought the audio from the police car as they were pulling him over said that he had a wide nose and looked like someone who had just committed a crime. So I don't know how you change your story to "I could smell weed from the car so I pulled them over."
Lastly, weed makes you hungry, happy, creative, and sleepy. So while he shouldn't have been driving if he was using, because driving under any substance is bad (especially coffee), he would have only been a threat to a McDonald's dollar menu.