the supreme court in 2013 or 2014 actually ruled that police cannot follow you in such a fashion to cause you to violate the vehicle code or other laws. The actual case in front of them was someone who was alternately tailgated then cut off by a police cruiser over the course of ~3 miles, and due to that did some traffic infraction. Once detained, a request to search was asked and granted and they found dozens of amphetamine pills. This happened in either Colorado or Utah.

The decision was a very good read but i haven't been able to find it since, because i want to get something removed from my record that happened a couple of months before the supreme court decision. Ford's "tap the signal" flashes your blinker three times, which is not enough flashes to be legal in any state i've ever lived in. However, i was being tailgated on a single lane divided highway for 5 miles, and once a lane opened up, i tapped the signal, waited three flashes, and moved over. Boom. Tickets galore. Reason for stop? I didn't signal enough.

It was like 01:30 and ourselves and the police were the only people on the road the entire time we were on it. There was no safety issue.

Anyhow, that's an example of what the supreme court said is not probable cause. You can't manufacture it by harassing someone in a vehicle for miles.