That your wife is a petite woman can certainly influence her ability to absorb and tolerate alcohol. And it may very well account for her poor performance on the field sobriety tests and on the breathalyzer. The enzyme that breaks down alcohol in the stomach is called dehydrogenase, and women have less of it than men. That can contribute to higher blood-alcohol concentrations in women than in men even if they have consumed the same amount of alcohol, or even if the man has consumed more alcohol than the woman. Another possible explanation is hormone levels, which affect the body’s ability to process alcohol. Because of this, many women will experience faster intoxication right before menstruation. Women also generally have a higher percentage of body fat and a lower percentage of water. And the less a person weighs, the more they will be affected by a given amount of alcohol.