In the State of California and many other states, one is determined to be driving under the influence with a measured blood alcohol contact of 0.08% alcohol/volume of blood analyzed. That may sound like a fairly insignificant amount of alcohol in a blood sample to decide that a person is unfit to drive a motor vehicle but when you look at the physical effects a slight amount of alcohol has on the human body, you can appreciate the standards established... Just as a side bar, one should also know that this applies to operating a motorcycle, airplane, boat and some other specified transportation vehicles.
I found it quite interesting when I came across the actual physical effects various amounts of alcohol has upon the human body. Now, of course, we understand that each of us react somewhat differently to stimuli than the next person, but this is the standard that the courts and law enforcement measure us by. Drinking enough alcohol to cause a bold alcohol concentration (BAC) of 0.03-0.12 typically causes a flushed red appearance in the face and impaired judgment and fine muscle coordination. A BAC of 0.09 to 0.25 causes lethargy, sedation, balance problems and blurred vision. A BAC from0.18 to 0.30 causes profound confusion, impaired speech, (e.g., slurred speech) staggering, dizziness and vomiting. ABAC from 0.35 to0.80 can cause a coma (unconsciousness), life threatening respiratory depression and possibly fatal alcohol poisoning. The transition from mildly impaired to a potential deadly ingestion of alcohol can progress fairly rapidly. Young people are especially endangered by these phenomena.
Depending on the jurisdiction, BAC may be measured by police using three methods--blood, breath and urine. For law enforcement purposes, breath is the preferred method since results are available almost immediately. The validity of the testing equipment/methods and mathematical relationships for the measurement of breath and alcohol, have been criticized. Improper testing and equipment calibration is often used in defense of a DUI.
Driving while consuming alcohol may be illegal within a jurisdiction. In some, it is illegal for an open container of an alcoholic beverage to be in the passenger compartment of a motor vehicle or in some specific area of that compartment. There have been cases of drivers being convicted of a DUI when they were not observed driving, after being proved in court they HAD BEEN DRIVING while under the influence.