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BAC tests: How reliable are the results?

During a traffic stop for suspicion of drunk driving, a police officer may ask you to participate in tests to determine your level of intoxication. The first of these tests typically include roadside or field sobriety tests, which determine whether you are intoxicated. However, police officers commonly use other tests following the field sobriety tests to evaluate whether your blood alcohol content (BAC) level exceeds the legal limit of .08%.

How accurate are these tests? In a DUI traffic stop, you may not even consider your options or question their accuracy. However, various complications can result in inaccurate results that can potentially worsen the penalties you face.

The accuracy of breath, blood and urine tests

Breath, blood and urine tests are the three most common methods of evaluating BAC levels in Illinois and across the country. Police officers most frequently administer breath tests. The necessity of having a medical professional administer blood and urine tests makes these tests less convenient and therefore less common.

Complications that can affect the accuracy of BAC tests include:

  • Lack of calibration and regular maintenance on breath test machines
  • Improper administration by the police officer, medical professional or more
  • Improper storage or labeling of blood or urine samples
  • Use of expired machines, kits or devices
  • The driver’s use of medications or other substances that can affect the results

As law enforcement officials consider urine tests to be the least accurate in determining BAC levels, breath or blood tests are more commonly used.

Can you refuse to take these tests?

Due to implied consent laws in Illinois, drivers consent to taking BAC tests by using state roadways. Because of this, refusing to consent to BAC tests can result in the automatic revocation of your driver’s license, in addition to potential criminal penalties. Additionally, law enforcement officials across McHenry County began seeking warrants for blood tests in 2018 when drivers refuse breath tests.

A conviction for a first-time DUI offense in Illinois can lead to steep consequences, including significant fines, jail time, probation, the start of your criminal record and more. After an arrest and the administration of BAC tests, immediately consider your legal options to fight the charges, question BAC results and reduce the penalties you face.