I would need to see much more detail. There's really no way that a cop is going to just blurt out to a motorist that he's investigating for drug trafficking. It will be a far subtler approach. He will ask a series of questions about travels and purposes thereto, and if he was armed with all of that information from Flock, he would have been comparing answers, if any, to recorded movements. He may ask the motorist to get into his squad car for the duration of the interrogation. Whether the motorist cooperates with all of the questioning or otherwise, he will then ask whether he can search. If the motorist consents to search, which most will do, there can be no allegation of Constitutional violation. So this motorist must have refused consent. If the motorist refuses consent, the cop will advise that the motorist is being detained for a dog sniff and that since it'll take awhile waiting on that to get there, does he still refuse search consent? If search consent continues to be withheld, the cop will seek to create an event sequence starting from reasonable suspicion to detain, which he will say was raised by the motorist answering suspiciously or merely appearing "nervous," to probable cause for search as provided by a positive drugs indication by canine. Of course, his buddy the dog handler will be sure to come away with such a positive regardless, as he controls the dog and interprets what the dog's "telling" him. And then after the ensuing search that turns up absolutely nothing illicit, the cop and his dog buddy will explain that the dog had detected "drug residue" and that the amount present was too small to collect as evidence.
All the while the motorist has been locked up in a cop car observing an increasingly frustrated and fruitless search of his car whilst wondering if the next shoe to drop is that they'll
"plant" something.
And then they will let him go, but not before asking him why he had put them through all of that by refusing to answer questions and/or refusing search consent.
