Arizona courts presume that DUI defendants with a BAC of 0.05% or below were not impaired by alcohol. But should the case go to trial, prosecutors can try to rebut this presumption by introducing evidence of impairment. If the defendant's BAC was above 0.05% but less than 0.08%, Arizona counts will not presume one way or another whether the defendant was impaired. Instead, it is up to the prosecutors at trial to prove beyond a reasonable doubt that the defendant was impaired. In short, it is an uphill battle for prosecutors to prove that DUI defendants with a BAC below the legal limit were impaired and therefore guilty. But it is possible.