Breathalyzers and Blood Alcohol Content


Although people use breathalyzer and blood alcohol content interchangeably, there is a very important difference. A breathalyzer doesn't read your BAC but estimates it. Breathalyzer test results can be far from 100% accurate and may be challenged in DUI defenses.

It is illegal in all 50 states to operate a motor vehicle with a BAC of 0.08% or greater. It's possible to be convicted of DUI even after passing field sobriety tests or not appearing impaired if your BAC is .08%. Following a DUI conviction, you may face many DUI penalties like license suspension, probation or jail time, with the possibility of a prison term.

Measuring BAC

Your BAC may be tested several ways. The breath test is the most common way to estimate BAC. Many police departments use portable breathalyzer testing devices to determine BAC. Some states don't allow test results from these portable breathalyzers, using larger machines that are generally considered more accurate. A urine test may also be used to estimate BAC.

While many states rely solely on breath or urine tests to estimate BAC, a blood test is the most reliable way to get an accurate result. A DUI lawyer can help you determine if you can challenge your breath or blood test as a DUI defense.

Problems with Breathalyzer Tests

Several problems exist with breathalyzers that could result in an inaccurate estimation.

  • Breathalyzers assume a specific ratio between BAC and breath alcohol content to make estimations. This 2100:1 ratio may actually range between 1700:1 and 2400:1. If a breathalyzer reads a person's BAC at .08%, their actual BAC could be between .065% and .09% - variation that could mean all the difference in a DUI case. Urine tests also make estimations based on an assumed ratio of 1.3:1, which may not apply for every person.
  • Breathalyzer machines are often confused by other substances that throw off BAC estimations. A breathalyzer machine tests for ethyl alcohol (ethanol) from alcoholic substances. It may misread many other substances in the human breath as alcohol content. Some breathalyzers become confused by acetone, which may be present in large amounts in diabetics and people with special diets. Breathalyzers have also been confused by fumes coming from certain paints and adhesives.

BAC, Breathalyzers and DUI Laws

If you've been charged with a DUI based on a breathalyzer or urine test, a DUI lawyer may be able to help you challenge those results. Fill out a free DUI case evaluation form or call 877-349-1311 to schedule a free consultation with a local DUI attorney today. Get legal advice on how to handle your DUI case.

The above summary is by no means all-inclusive and is not legal advice. For the latest information on breathalyzer and BAC issues, speak to a DUI attorney in your area.