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Convincing Evidence Or A False Alarm? Understanding BAC Results

30 November 2019 by Kenneth Graham

It takes good evidence to form successful legal cases and a driving under the influence (DUI) case is no different. The blood alcohol concentration (BAC) result is heavily relied upon to provide that evidence in almost all DUI cases but it's far from a sure thing. Read on to find out more.

Why BAC Evidence Matters

DUI cases can be complex and there's plenty of room for issues with evidence to arise. In some cases, you can be convicted based on any number of things that happen just before and during the arrest. Some of that can include:

• Your driving behavior before the stop, as evidenced by the officer's observations and by their body and dash cams.
• Your behavior once the stop is made.
• The results of any number of field sobriety tests.
• The results of blood tests such as the portable breathalyzer, the breathalyzer at the station, and a blood draw at a medical facility.

Nearly every one of the above can provide unreliable results because of personal perceptions, the roadside environment, the defendant's physical and mental issues, and more. The BAC, however, is known to be the most reliable of all forms of evidence leading to a DUI conviction. This king of all evidence, however, is not without its own problems.

What to Know About BAC

While things can vary from state to state when it comes to a lot of things, the BAC legal limit is the same for all states except Utah: .08%. Testing at or above .08% means you are considered legally drunk and can be arrested and charged with DUI. The BAC test uses the expelled breath of a driver to test the level of ethanol present. At first glance, testing at this number appears to be pretty strong evidence of intoxication – but is it really?

Problems with BAC Results

Just like other aspects of DUI testing, BAC test accuracy can vary depending on several factors. The age, sex, weight, and other issues of the defendant can put the arbitrary .08% number in question. The accuracy of the testing equipment can be questioned too. Your DUI attorney will ask to see the calibration records for the machine and find out if the officer who performed the breathalyzer was qualified to do so. Finally, there's a theory in DUI testing known as the rising blood alcohol defense. In a nutshell, this defense points out how the blood alcohol level lags behind the ingestion of alcohol. That might mean a person is not as inebriated as the results indicate depending on when the stop and testing occurs.

Speak to a drunk driving attorney to find out more about the many ways you can fight against your DUI charges.

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