I have never seen a police report say that a California DUI suspect “passed” the field sobriety tests performed after a DUI stop. Does that mean that all of those suspects were intoxicated? No.
This necessarily means that people can fail field sobriety tests while sober. But how?
Field sobriety tests are notoriously unreliable. Yet law enforcement agencies continue to employ the Horizontal Gaze Nystagmus (HGN) Test, the Walk-and-Turn Test, and the One-Leg Stand Test to determine intoxication. These are the tests that the National Highway Traffic Safety Administration has designated as standard. Other tests include the Rhomberg Balance Test, the Finger-to-Nose Test, and the Finger Tap Test.
Field sobriety tests are used to gauge a person’s coordination, balance, and simple motor skills after they have consumed alcohol. And while they may, in fact, test coordination, there are a number of reasons why a sober person might fail a field sobriety test.
Needless to say, most people are both stressed and nervous when they are pulled over and asked to step out of their vehicle. The stress and nervousness inevitably make it difficult to concentrate. Yet officers regularly fail a person for having trouble following the field sobriety test instructions.
A person who is intoxicated may likely exhibit trouble with balance. Lack of balance is what officers look for when a suspected drunk driver performs field sobriety tests. However, balance can be affected by many things, one of which is inner ear problems. The inner ear contains a small organ called the labyrinth that helps us maintain balance. When the labyrinth is disrupted, so too is that person’s balance. Some of the things that can disrupt the labyrinth include infections and illness, head trauma, age, and tumors, to name a few.
Physical problems and disabilities can also affect a person’s performance on field sobriety tests. Physical problems such as knee pain or lower back pain may make it difficult to, say, walk heel to toe in a straight line or stand on one leg perfectly still for 30 seconds.
For the same reasons, people who are older or who are overweight may also have trouble performing field sobriety tests that require coordination and balance.
While it may be dangerous to drive while tired, it is not illegal like driving under the influence. However, lack of sleep can cause many of the same symptoms as intoxication. When people are tired they can experience poor balance, lack of coordination, and trouble with motor skills. What’s more, when someone is sleep deprived and tired, they exhibit bloodshot, watery eyes. Unfortunately, bloodshot, watery eyes are amongst law enforcement’s favorite indicators of intoxication.
Perhaps one of the most powerful factors affecting a person’s purported performance on field sobriety tests is the officer’s interpretation of that person’s performance. Law enforcement officers have already decided that a person is intoxicated even before the person performs the field sobriety test. As a result, the officers are going to see what they expect (or want) to see.
I could go on with many other reasons why sober drivers fail field sobriety tests, but that would make this post extremely lengthy. Suffice it to say, field sobriety tests are unreliable and sober people do fail them.
Having said that, drivers have a right not to and should not ever agree to perform field sobriety tests because they will fail whether they were intoxicated or not.