greyham28 wrote: I definitely wouldn't trust this thing. Or, for that matter, the breathalyzer the police use.
I can't speak for other agencies, but in my city, the breathalyzer is "calibrated", and tested monthly. I think it is state law that it is tested regularly. I have seen people take several tests in a row just to verify results, and I never saw a variance of more that .002%.
As far as you getting a dui at .051, I can only speak for my city, but I think the rules are similar around the country. The "State" has a limit of .08, to be charged with a "state" dui. This only means that over .08, the state can suspend your license. However, there are other limits in my (and most other) city that if you blow over .05, you can be charged with a "municipal" or "city" dui. With this, there is no action taken by the state to suspend a DL. It is important to note that for a person who is between .05, and .08, the suspect has to show "impairment" and the officer has to be able to articulate it in court (ie: failing field sobriety tests, erratic driving, etc.). So, although you must be over .08 for a dui that may cost you your license, blowing over .05 can still get you a dui, but you get to keep your license.
Also, my state and most others have a "Zero Tolerance" for anyone under 21. In Missouri (my state), a person under 21 only has to blow above .02 for a dui charge. This is about 1 beer for most people.
Hope this clears up your situation a little, feel free to ask questions and I'll help to answer as best as I can.
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