Presently stoned means nothing. Are they under the influence and incapable of operating a motor vehicle? Yes you can determine that with sfst's. Standardized field sobriety tests test many things, including one's ability for divided attention tasks, IE requiring someone to do multiple tasks at once (walk and turn and one legged stand). HGN is easy with someone on weed as they will have all the physical cues of being high without hgn, and they will usually have lack of convergence. That's a clue......
dui's are a totality of the entire investigation. Why was the stop made? Moving violation? Crash? Equipment violation? What are the behavioral ques? What is observed inside the vehicle? Etc.
It depends on the state for the threshold for a Marijuana dui (usuallystates that have legalized weed). Some have a specific cannabinoid measurement that determines whether someone is dui. Other states simply go by the incapable of operating a motor vehicle wording.
NEVER do sfst's. EVER. NEVER talk to LE without an attorney. Sfst's are a joke administered by a clown who thinks there few weeks of "training" quality them as a medical DR. Any lawyer will tell you that. And NEVER help them to do a roadside inspection(turn signal, lights, ect.)
