Accuracy of Field Sobriety Tests Challenged

Stephanie Stout May 5, 2015

Field sobriety tests are not always accurate. Those with mental or physical impairments or difficulty balancing may fail a field sobriety test.

Any time of the year - and especially during peak drinking periods during the holidays - law enforcement officers in Colorado may be seen directing drivers to take field sobriety tests. These tests have been developed to assist officers in determining if someone has been driving drunk. Police officers rely on their individual judgment, rather than the results of a breath, urine or blood test, to decide if the person they pulled over has been drinking or not. This practice may result in an innocent person being accused of a crime.

What assessments are given during a field sobriety test?

Authorities developed three separate tests to be used in the Standardized Field Sobriety Test, states the National Highway Traffic Safety Administration. A subject is asked to perform these tests during a traffic stop. They include the following:

  • Horizontal gaze nystagmus test - The involuntary jerking of a driver's eyes may be pronounced with intoxication, so officers will look at a subject's eyes.

  • One-leg stand - The driver will be asked to stand on one leg without putting the other foot down and count out loud for 30 seconds.

  • Walk-and-turn - An officer will have the driver walk in a straight line, then turn around on one foot and walk back in the same direction.

Losing one's balance, holding the arms out or failing to follow instructions properly may negatively impact the subject's standing in the field sobriety test.

Can sober people fail any of the tests?

The tests may seem simple in theory, but many people find them difficult to perform despite not having anything to drink. According to ABC Action News, someone might not pass a field sobriety test if he or she has a medical condition that affects balance, is injured and can't walk straight or has a cognitive condition that affects speech or the ability to comprehend directions. There are numerous physical and mental impairments that might affect balance or otherwise mimic the signs of intoxication, despite the person being completely sober.

Is a field sobriety test very accurate?

Three sober people at a shopping center agreed to take a field sobriety test as an experiment, reported NBC 29 News. Although all three passed, two of them said they had problems balancing and the third said she was so sleep-deprived that she mistakenly didn't follow directions. They admitted that any of them may have been charged with intoxication if an officer had been conducting the test, especially if they had been nervous or feeling pressured.

It has been reported that the horizontal gaze nystagmus test is only accurate 77 percent of the time. The walk-and-turn test is said to be accurate in 68 percent of instances, while the one-leg stand is the least reliable at just 65 percent accuracy.

It is easy to understand, therefore, how someone may end up with a drunk driving charge despite being sober. An experienced Colorado DUI defense attorney may be able to assist after an arrest.