BAC is the blood-alcohol concentration in a person's blood. It is expressed as a percentage. It is sometimes referred to as blood-alcohol content. The BAC is often the critical evidence in a DUI investigation. There is a presumption in every state that a BAC of .08 or higher is per se proof of impaired driving or DUI for driving a car on a public road.
For people under the age of 21 in Tennessee the BAC presumption is .02 or higher for proof of impairment. For commercial drivers a BAC of .04 or higher is proof of impairment.
Blood-alcohol concentration (BAC) can be analyzed in two ways: blood draw or breath test. It is expressed in percent weight by volume (% w/v) based upon grams of alcohol per 100 cubic centemeters of blood or per 210 L of breath. A BAC of 0.08 % w/v means 0.08 g of alcohol per 100 cm³ of blood (0.008g/100cc) or 0.08 g of alcohol per 210 L of breath.
Failure to submit to a BAC test, blood or breath at the officers discretion, in Tennessee will result in a one year loss of license. A restricted license may be granted by the court in some circumstances.
Incidentally the BAC levels for DUI in other countries is: China .02, India .03, Norway .02, England .08, France .05.
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