Legal Question in DUI Law in California

When arrested or charged with any crime, the proper questions are, can any evidence obtained in a test, search or confession be used against you, and can you be convicted, and what can you do? Raise all possible defenses with whatever admissible and credible witnesses, evidence, facts and sympathies are available for legal arguments, for evidence suppression or other motions, or at trial. Effective plea-bargaining, using those defenses, could possibly keep you out of jail, or at least dramatically reduce it. Not exactly a do it yourself project in court for someone who does not know how to effectively represent himself against a professional prosecutor intending to convict and jail you. If you don't know how to do these things effectively, then hire an attorney that does, who will try to get a dismissal, diversion, reduction or other decent outcome through plea bargain, or take it to trial if appropriate. If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me.

There are basically 3 levels of police involvement - a consensual encounter, a detention and an arrest.

They don't need any evidence or legal justification for a consensual encounter - they can just walk up and talk to anyone they want as long as they're in a place they have a legal right to be and the person they're contacting is truly free to leave (and a reasonable person would think that in that scenario the person was free to leave).

In order to justify a detention, they must have reasonable suspicion of criminal activity. They must point to some law they reasonably suspect was being committed - even if it was a simple traffic violation. From what you wrote, they don't have a "crime" or a violation of any sort they can point to, making the traffic stop very, very questionable.

If the detention is unlawful, then the observations, blood alcohol results and any statements are out. Without those, they have absolutely no case.

The details and facts of the case, including the police reports, dispatch logs and tapes and video (if any) will need to be reviewed in depth, but it sounds as though you have a decent motion to suppress.