The officer can testify, however it's usually not a reliable test and the police don't hang their hat on it.
What is more likely to cause issues is any weaving, erratic behavior, crossing double yellow lines, speeding, etc.
Then once the officer has you pulled over, he's likely to testify that either A) you had beer in the car or B) you smelled like alcohol. Once he says those magic words, it's off to the races.
You should get a qualified DUI attorney immediately. We can explain these issues to you in depth.
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