When a police officer pulls you over because they suspect drunk driving, there are usually two kinds of evidence that will help build their case. One will be their personal recollections and written report about the situation. The other will be any physical or chemical evidence gathered from you during the traffic stop.
When the state claims to have authoritative evidence, you may not feel like you have any options to defend yourself. However, it might be possible for you to challenge the evidence state has against you.
Human understanding and recollection are both flawed
Police officers conducting a drunk driving traffic stop will likely see what they want to. In other words, they might interpret behavior with other reasonable explanations as signs of impairment.
What could be the aftereffect of a long, tiring day or the consequence of a medical condition might seem like an impairment to an officer. Additionally, when they recall the traffic stop, they might mentally exaggerate some of what happened in order to internally justify their arrest of you.
If you can provide alternative explanations for behavior or show that the officer misrepresented your behavior during the traffic stop, that may undermine their evidence against you.
Chemical breath tests produce bad results all the time
Physical or chemical evidence is now the gold standard for criminal proceedings. Officers use chemical breath tests to help establish chemical proof of impairment. Unfortunately for them but fortunately for defendants, the science behind how the devices work makes false positives very likely. Lack of maintenance can also cause accuracy issues.
You could potentially challenge physical evidence much like you could testimony. Exploring the evidence the state has against you is usually the first step toward developing a criminal defense strategy.