The best defense in your drunk driving case is winning your refusal case. By winning the refusal, you take that argument away from the prosecutor. This means that the key to winning the drunk driving case is winning the refusal case. While judges often rely on the police observation of FSTs as justification for an arrest, the evidence needed to arrest is a lot less than that needed to convict. Eliminating the refusal evidence can leave the prosecutor without any concrete evidence and, consequently, without a case.
Most people think that the only issue in a drunk driving case is whether the driver was intoxicated.
In fact, whether the driver was intoxicated may not matter at all. The first issue in any drunk driving case isn't whether the driver broke the law. It's whether the police broke the law. Many drunk driving cases turn on the conduct of the officer, not the guilt of the driver. If police obtain evidence of guilt illegally, in violation of the driver's Constitutional rights, then that evidence is not legally admissible and cannot be used against the driver in court.