It's impossible to tell you if that is a good defense because we have no idea what the details of the report are, as well as how the various forms are filled out. Was the breath machine even working properly? What objections will you be making to the dmv's evidence? Was it even a lawful stop?
There are so many different ways to attack this, you really need to hire someone with the experience to do it.
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As my colleagues observe, there are many facets to presenting a credible defense at a DMV hearing. From what you state, you may certainly assert your factual defense and the cop will testify as to the accuracy of his police report. It will then be a question of credibility for the hearing officer.
Be aware, though, that a police officer need only ask you once about taking a chemical test. If you say no, or even say nothing, he can note this as a refusal and is under no obligation to give you a second chance, even if you ask for one.
You definitely have a case worth fighting. However you stand little to no chance if you attempt to represent yourself at a DMV. Hire an attorney to fight for you. Best of luck.
It's certainly a defense. Whether it is a good defense requires a full investigation of the case with your attorney.
I wish you the best of luck in this matter.
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