What Is a Field Sobriety Test?

Sobriety test paperwork on a desktop. Stamped with a FAILED.

Field sobriety tests aren’t really “tests” in the traditional sense. Rather, they are tools used by local law enforcement to determine whether a person may be driving under the influence.

In your typical DUI case, the law enforcement officer will observe a traffic violation, such as speeding, careless driving, or disregard for a traffic device, then pull someone over. From the moment that the officer steps toward the driver, the office is looking for certain signs of impairment. The most obvious is smell, whether it be of alcohol or marijuana. Other signs can include slurred speech and red eyes. Once the officer observes one of these indicators, then he will likely ask the driver to step out of the vehicle. This is usually done for two reasons: 1) to further determine if the person may be impaired, and 2) to begin giving a field sobriety test.

There are three standard field sobriety tests used by law enforcement in Mississippi. The walk-and-turn test is where the driver walks nine steps, heel to toe, in a straight line. The driver usually passes this test by going the nine steps, turning around on one leg, and returning back in nine steps, heel to toe. This test is used to see if the driver can follow basic directions and walk in a straight line without stumbling.

The one-leg stand test is where the driver stands on one leg for several seconds while counting. This tests the driver’s balance and ability to follow directions, and the officer will usually look for the driver waving her arms to maintain balance or putting a foot down too early.

The third test is the horizontal nystagmus gaze (HGN) test. In this test, the officer uses a pen or light and asks the driver to keep their head still and follow the light with their eyes. During this test, the officer is looking to see whether the driver can follow directions; however, more importantly, the officer is looking at each eye to see whether there is a slight involuntary jerking of the eyes, which is an indicator of possible impairment.

So how accurate are these tests? While officers and prosecutors would have you believe that these are clear indicators of impairment, they are not. These tests are not necessarily proven to be scientifically accurate. Rather, failing one or all of these tests could simply indicate poor balance, the officer’s poor explanation of the directions, and underlying health conditions.

For example, suppose that Joe is pulled over for a DUI. Joe had knee surgery several years before, which means that he would have difficulty standing on that leg or could possibly have trouble putting his feet heel to toe. Depending on whether Joe has an underlying neurological condition (which many people suffer from), he could also “fail” the HGN test.

But here’s the interesting part: drivers have the right to refuse a field sobriety test. When an officer stops you, you must cooperate when it comes to providing basic information, such as your name. While there is some case law that says that a driver should step out of their vehicle when requested by an officer, beyond that, a person has no obligation to do anything else. The thing to remember is that the less information that you provide to a law enforcement officer, the less likely that you will be charged with a DUI, and the greater the likelihood that if you are charged, you could be found not guilty.