Tennessee Criminal Defense

The Reliability of Field Sobriety Tests

In order for law enforcement personnel to make a DUI arrest, they must first establish what is known as “probable cause.” Essentially this means they must reasonably suspect that you are breaking the law by being intoxicated while driving. However, they must establish this suspicion through legally acceptable means, and they frequently use widely-accepted field sobriety tests to do so. Many people know of at least one of these sobriety tests, and most people think they’re either highly accurate or even infallible. However, those same people are often stunned to learn the truth: field sobriety tests are notoriously inaccurate and provide false positives leading to unlawful arrests fairly frequently. Let’s look at how some of the most common field sobriety tests work and see how often they are inaccurate.


Back in the late 1970s, the NHTSA and the Southern California Research Institute were tasked with determining which field sobriety tests were the most accurate in an attempt to reduce the number of errors and false arrests. After extensive testing, researchers determined that the three most accurate tests were the walk-and-turn test, the one-leg stand test, and the horizontal gaze nystagmus test.

However, even when all three of these tests are administered together and done properly, they were still only correct 82% of the time. That’s nearly one in five instances being a false positive leading to an arrest! Used individually, these tests are even more inaccurate, which could factor heavily in your case.


The walk-and-turn test is perhaps the most well-known field sobriety tests. This test essentially requires you to divide your focus by walking in a straight line and turning while listening to instructions given by the administering officer. You will be required to take nine steps in a straight line, heel-to-toe fashion, then turn on one foot and walk the opposite direction. This test used to be horrendously inaccurate, and even with standardization, its accuracy rose to just 68%.


The one-leg stand is a particularly difficult task for many people to do successfully even while completely sober. In this test, you will be required to stand on one foot with the elevated foot about six inches off the ground and your toes pointed forward. You will then have to count out thirty seconds. However, many people don’t have the physical ability to successfully complete this test—it’s not a simple task after all, particularly for those who don’t have good balance in the first place. Standardizing increased this test’s accuracy as well, but only up to 65%, meaning it’s only correct a little over half of the time!


This is perhaps the most accurate test in that it doesn’t require any difficult physical activities and is the most difficult for an intoxicated individual to pass. This test essentially is a test for nystagmus, which is a condition where the brain loses the ability to properly control eye muscles when intoxicated by drugs or alcohol. Officers test this by simply holding up a pen or their finger and then asking you to follow it with your eyes without moving your head. If your eyes rapidly jerk back and forth while following the target, then the officer will suspect you are intoxicated. While this test seems almost foolproof, it’s not infallible. Even with standardization, the accuracy only rose to 77%.

Because these tests are notoriously unreliable, your arrest may not have been made on legal or justified grounds. For this reason, you should not hesitate to speak with a Murfreesboro DUI lawyer who can help you fight back against your charges. When you call Crain & Flatt Attorneys at Law you can trust that you have a skilled and experienced legal advocate taking care of your case with your best interests at heart. Attorney Crain has proudly obtained a 10.0 Superb rating from Avvo as well as been named a Top 100 Trial Lawyer by The National Trial Lawyer twice thanks to his years of dedication to his clients, exceptional legal ability, and unwavering ethical practices.

If you or a loved one are facing DUI charges, don’t delay! Let Crain & Flatt Attorneys at Law​ review your case today! Call our office at (615) 200-9409.

All accuracy statistics courtesy of FieldSobrietyTests.org.