Blood Alcohol Content (BAC) is the percentage of alcohol present in a person’s bloodstream as they consume liquor, beer, or wine. There are several methods used to determine a person’s BAC, though most agree the best results are revealed in a blood test. Legally acceptable estimates are also determined through a breathalyzer.
Both methods are used by law enforcement agencies throughout the Commonwealth of Virginia. Handheld breathalyzers, which officers may use during a DUI traffic stop, often are not as reliable. They are, however, useful for police in determining probable cause to administer a blood or breath test.
There are many legal challenges a skilled Virginia DUI defense attorney can make if probable cause was not adequately or legally established before the blood or breath tests were administered, or if the device or devices have not been properly calibrated and maintained.
If you have been charged with DUI/DWI in Virginia, contact Karin Riley Porter and the team of Virginia criminal defense attorneys she leads. For a general primer on understanding and estimating your BAC, please read further.
• Weight – The more a subject weighs, the more alcohol he or she may be able to consume before registering the effects of intoxication.
• Body Fat – The higher your percentage of body fat, the more alcohol your body stores – and the longer it takes to purge alcohol from your body.
• Metabolism – The higher your metabolic rate, the faster your body processes alcohol.
Another factor to consider when estimating your BAC is the alcohol content of your chosen beverage. The following is based upon the assumption that you will drink only one classification of the three types of alcohol listed below.
• Beer – Is generally four to six percent alcohol; though the percentage – or proof — depends upon the type of beer. Some imports and micro brewed beers are stronger (generally eight to 12 percent), though a few have been known to have even higher concentrations of alcohol.
• Wine – One five ounce glass of any type of wine (white, red, rose, or champagne) usually contains about seven percent alcohol, though again, variations do occur depending on variety and region.
• Distilled alcohol or liquor – Has the greatest variation in proof. Many types of liquor consist of 40 proof. But some types of alcohol are far more potent.
Calculating your BAC also depends on your gender, age, and – as previously mentioned – your weight. Men and women absorb alcohol differently due, in part, to women being deficient in an enzyme that helps metabolize alcohol. Researchers were able to identify the enzyme in 2001, proving a long-held theory that women are more susceptible to the negative effects of alcohol. You can read about the study in Scientific American’s online edition.
The average person can metabolize one standard drink per hour, though that timeframe may be slightly faster for those with higher tolerances. The amount can vary slightly depending on your weight and percentage of body fat, how much you’ve had to eat and sleep, and several other factors. On average, however, one standard drink raises a women’s BAC by .02 and a man’s BAC by .017.
For a more accurate estimate, you may want to use an online blood alcohol calculator or refer to a blood alcohol concentration chart, like the one provided by the California Department of Motor Vehicles here.
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