What are Field Sobriety Tests Designed to Show?

If a police officer suspects that you are driving impaired, he or she will request that you complete a field sobriety test. A field sobriety test (FST) is designed to show a person’s level of impairment during a DUI stop. The test has three components: a horizontal gaze nystagmus test, a walk-and-turn test, and a one-leg stand test. Field sobriety testing is a standard procedure for law enforcement, assessing a person’s cognitive and physical capabilities. This allows the officer to gather the necessary information to establish that you were driving under the influence.

Even failing one FST may result in a DUI arrest. If you or a family member has recently been arrested for a DUI, reach out to our Nashville DUI lawyers.

Breakdown of Field Sobriety Tests

Each FST is designed to test specific neurological or physical impairments:

Horizontal Gaze Nystagmus

During a horizontal gaze nystagmus (HGN) test, the police officer will move a penlight or object from side to side, asking you to track the object with your eyes. Law enforcement will assess whether you can track the object smoothly. If you are inebriated, you will begin to show signs of nystagmus (your eyes will make a “jerking” motion). The officer will evaluate if distinct nystagmus is present when you are looking entirely to the side (maximum deviation) and the onset of nystagmus prior to 45 degrees. During an FST, maximum deviation is held for at least four seconds to monitor if nystagmus is present. Difficulty visually tracking an object may be a sign of nervous system depression from alcohol consumption.

Walk-and-Turn

During the walk-and-turn test, the officer will ask you to take nine steps in a straight line. You must take nine steps heel-to-toe, then reverse direction. When turning around, you must pivot on one foot while holding your hand to the side. Trouble with balancing may be a sign of motor skill impairment.

One Leg Stand

You will be asked to balance on one foot, with the other foot six inches off the ground. You will be asked to count, keeping your foot in the air the entire time. Swaying or falling over may indicate balance issues or problems with multitasking.

Challenging the Results of a Field Sobriety Test

Tennessee’s legal limit is 0.08%. So, if your blood alcohol content is 0.08% or greater, then you are considered impaired regardless of your behavior behind the wheel. However, the results of an FST do test behavior, which can be impacted by various elements. While a standard FST may highlight neurological or physical deficits, environmental factors can cause a sober person to appear inebriated.

Uneven ground can cause a person to have balance issues, while poor lighting can cause issues with visually tracking an object or walking in a straight line. Law enforcement may claim that probable cause is established based on these test results alone, not diving deeper.

Keep in mind that FSTs do not measure a person’s baseline, just how well they complete the tasks. Various medical conditions can also impact a person’s cognitive and motor skills, causing someone to fail any one or more of the FSTs. For example, medical conditions that impact the inner ear can cause someone to have trouble balancing on the walk-and-turn test. These potential conditions include Parkinson’s, Ménière’s disease (chronic ear disorder), and vertigo.

Additionally, age and weight can play a major factor in how successfully you complete these tests. Unlike a declining breathalyzer or blood test, under Tennessee law, you will not experience any legal penalties for declining an FST. Given this, our legal team recommends that you decline performing field sobriety testing during a DUI stop.

Contact Our Nashville DUI Lawyers Today

Although field sobriety testing is intended to show a driver’s impairment, it can make a sober driver appear impaired. At Andrew C. Beasley, PLLC, our Nashville DUI lawyers routinely question whether police officers are using best practices in administering FSTs. If there is reason to believe that a police officer did not follow appropriate procedures, we will question the validity of the field sobriety test results.

To arrange a free consultation with one of our Nashville DUI attorneys, our office can be reached online or by phone at (615) 846-9889.