When a driver is charged with exceeding the legal limit, blood alcohol content (BAC) is essential in a driving under the influence (DUI/DWI) arrest. The blood or breath alcohol level will prove to be some of the most damning – or exonerating – evidence against them. For those who are arrested for suspicion of drunk driving with a chemical test result that exceeds the legal limit – .08 percent in all 50 states – there are many ways to challenge the accuracy of these tests.
However, even where it is conceded that the chemical test of the blood, breath or urine sample is accurate, these test results only reveal the subject’s alcohol level at the time of testing, not at the time of driving. It is the condition at the time of driving that is of ultimate concern in DUI / DWI cases; the chemical test is only relevant to the extent that it allows those concerned to look backwards in time and estimate alcohol level at the time of driving.
In order for the prosecution to meet its burden at the time of trial, an expert will testify about alcohol absorption, distribution, and elimination in the human body. Many authoritative articles have been written on the subject, most notably those by Kurt Dubowski and A.W. Jones. Because of the variables in the subjects taking the test, such as metabolic rate, as well as variations in conditions, such as stomach contents and drinking patterns, it is exceptionally difficult to look backward in time to pinpoint BAC at an earlier time. This difficulty increases with the passage of time, and becomes increasingly speculative. This provides an invaluable opportunity for an experienced DUI attorney to demonstrate reasonable doubt.
When a person drinks alcohol, it goes first into the stomach, and then into the small intestine, which is where most of the absorption takes place. Alcohol takes time to be absorbed in to the blood stream. The type of alcohol consumed, as well as the stomach contents prior to and during drinking, will impact the speed at which absorption takes place. Police will often ask a driver suspected of DUI when the last time the driver ate was, and what that individual ate. Statements will be put in to the police report and can be used to impeach your testimony at the time of trial if later change your story.
Alcohol gets metabolized immediately; however, the body cannot eliminate alcohol as quickly as it is absorbed. This is how an elevated alcohol level is created in the first place. Basically, the level of alcohol increases because absorption occurs faster than elimination. Absorption continues after drinking ceases. This will result in an increasing alcohol level, followed by a peak or plateau. This peak or plateau level is where there is perfect equilibrium – absorption and elimination occur at the same rate, so the alcohol level flattens out and is consistent for a period of time, usually 15 to 45 minutes, depending upon stomach contents and metabolic rate.
After the peak or plateau period, the individual will enter into the pure elimination phase. Here, so long as no additional alcohol is consumed, the alcohol level will steadily decrease at a rate of approximately .02 percent per hour. However, this will vary widely from person to person and in situation to situation.
Alcohol absorption and elimination can be affected greatly by drivers’ metabolic rates, eating patterns, fatigue levels, and many other factors. Typically, a police officer’s roadside investigation is not thorough enough to effectively address these issues. This information is extremely valuable in the hands of a well-trained criminal defense lawyer, who can devastate the prosecutions DUI/DWI case by effective cross-examination on these issues.