Drunk driving can be easy to prove for the state if the Breathalyzer reading is.08% or higher (.04% if you were driving a commercial vehicle with a CDL), and they can get that reading into evidence.
In order to do that, they must observe you for an uninterrupted period of 20 minutes, then immediately take the breath samples. This is to insure that the reading is not thrown off by any residual effects of alcohol in the mouth. The state must provide testimony by the observing witness that you did not
- Swallow anything
- Use chewing gum or tobacco
- Put any foreign object into your mouth
If any of this happens, they have to start the observation period all over again. Otherwise, the reading can be throuwn out.