The only way to find out is to hire a good attorney, get full discovery and evaluate the reason for the stop. A lawyer can determine if there is a good faith reason to challenge the stop. If that is bad, everything that flows from it is no good and the case can get tossed. You'll never figure it out on your own. Police do the wrong thing all the time and when chalenged correctly, their cases can go away.
If the police have a procedure in place that they will videotape all DUI's, and they did not videotape yours, you may be able to file a Motion to Suppress field sobrety exercises.
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