Drunk driving statutes across the country are not always uniform in how they describe the degree of inebriation that is required for conviction for driving under the influence (DUI) and
driving while intoxicated (DWI). However, they do generally provide that it is unlawful to have an excessive blood-alcohol concentration at the driving of driving – not at the time of being
tested. The statutes in most states provide provisions for a per se illegal offense when a motorist's blood-alcohol level is at or above 0.08%.
As it often takes between 45 minutes and three hours for alcohol to be absorbed into a person's system, a motorist's blood-alcohol concentration may continue to rise even after the motorist has been stopped or arrested. Anyone who has been arrested for DUI or DWI knows that it frequently takes an hour or more after the initial stop before a chemical test, such as a blood, breath or urine test, is given to the motorist. Therefore, even if the motorist's blood-alcohol concentration was only at 0.07% when he was stopped, by the time the motorist is tested the blood-alcohol concentration may have risen up to 0.12%. In effect, the chemical test will show that the motorist's blood-alcohol concentration was above the legal limit when it was actually below the legal limit at the time the motorist was driving. Conversely, a motorist may be intoxicated when he is driving and is stopped, but if he is no longer absorbing alcohol into his system, as the time elapses before the test, his blood-alcohol concentration will drop.
Most states have legislation that creates a presumption that the blood-alcohol concentration level found at the time of testing is the same as when driving, as long as the test is done within a set time limit. In other words, the statutes ignore the science of rising blood-alcohol concentration and hold that the blood-alcohol concentration level found in the chemical test is accurate for the time when the motorist was driving. This means that the motorist has the burden of proving, generally through the use of a toxicology expert, that his or her blood-alcohol concentration was actually lower at the time of the initial stop.
Copyright 2012 LexisNexis, a division of Reed Elsevier Inc.