In Wake County District Courts, if a blood alcohol concentration is admitted into evidence, and there is no good explanation (other than alcohol) offered by the defense to explain the number, then the number will generally be taken as sufficient evidence that the person was impaired.
In DWIs where a person has been stopped by police, and is soon thereafter brought down to the Wake County Detention Center for an Intox EC/IR II breathalyzer sample, and the sample is a .10 or above, then it is difficult to argue that the number doesn’t reflect impairment. In many cases, absent a medical explanation or problem with the machine, the person will be found guilty.
.08 and .09 results are somewhat different. In these circumstances, depending on the conduct, it may be possible to show a judge that the number is inaccurate.
The truth about the machines is that they are deeply flaw devices, relying on outdated technology to generate results that are then accepted as gospel by judges and, sometimes, juries.
But most judges are insufficiently aware about the problems with these machines. And most judges wrongly take the results of the machines as proof that a person was impaired when, in fact, the machines are affected by temperature differentiations, electronic interference, mouth alcohol (that is not detected by the IR component of the machine) and medical conditions that may have been unnoticed by the driver / defendant.
It’s still possible to win naked .08s and .09s because judges at least will allow that the machines are not pinpoint accurate. A person whose field sobriety tests are perfect, and whose driving is generally very good, may win a .08 or .09 case with an effective DWI lawyer.