Driver commits traffic violation and admits to smoking synthetic earlier (officer says he can smell it). Nothing in plain sight. Officer does not note any facts leading to believe passenger is in possession of anything illegal (no furtive movements, no nervous behavior, etc). After several minutes, the passenger is approached and told either consent to search of person or be arrested. Without any articulable facts to connect passenger to illegal activity, is there any authority to search the person of the passenger? I'm not finding any case law on point. Any help would be much appreciated.

You can probably make an argument based on the smell.

Garcia v. State, 2013 WL 3326027, at *2 (Tex.App. -- Corpus Christi June 27, 2013, no pet.) (not published) ("We first note that the odor of marihuana coming from a car is, alone, sufficient to give an officer probable cause particularized to every person in the car. See Jordan v. State, 394 S.W.3d 58, 64 (Tex.App.-Houston [1st Dist.] 2012, pet. ref'd)").

I agree that based on Jordan the officer did not need consent to search the passenger on those facts. Which is good, because you can't get consent by threatening them if they don't give it to you.

So the consent wouldn't be legal, but I think you've got facts that are sufficiently attenuated from the illegally obtained consent that would make the search constitutional.

Or Carroll? If officer has PC to believe synthetic weed is in the vehicle (which is sure sounds like he does), he has PC to search anywhere in the vehicle where said contraband could be secreted, which would include the passenger.