Do not assume that an officer needs evidence to make a traffic stop. They don’t. All they actually need is reasonable suspicion. This is a much lower standard and can be met when you have not actually done anything wrong.
For instance, say you are driving with your child in the car. The child, who is just old enough to ride in the front seat, accidentally bumps the rear-view mirror. You reach up to fix it. As you do so, you drift over the center line since your attention is momentarily diverted from the road.
A police officer sees this and decides that you may be drunk. They can legally pull you over to investigate whether or not you are. You have exhibited the type of behavior often seen by drunk drivers, and that’s all that the evidence the officer needs to conduct the traffic stop.
Of course, the opposite of this is also true, in that an officer without reasonable suspicion cannot legally carry out a stop. These stops would be little more than random and, therefore, would infringe on the rights of those stopped.
For example, you may be driving home from work at 2 a.m. The officer knows that the bars just closed down and that drunk drivers may be out. If you’re driving flawlessly, though, they can’t pull you over just to check and see if you’re drunk. The time of day is not enough to give them the type of reasonable suspicion that is needed.
If you get a DUI and you think that the officer had no right to stop you, you need to know what defense options you have to dispute the charge(s).