Field Sobriety Tests

When you are stopped by police and you are believed to be driving under the influence of alcohol or drugs the police officer will ask you to perform a variety of Field Sobriety Tests.  The Field Sobriety Tests (FST’s) are used to test motor skills, your divided sense of attention skills, and the ability to process information.  In other words, they are tests used by law enforcement to determine if your driving abilities are impaired by drugs or alcohol.

The Field Sobriety Tests were developed as a result of research sponsored by the National Highway Traffic Safety Institute and conducted by the Southern California Research Institute. What drivers don’t know is that there are only three FST’s that are recognized as Standard Tests by the National Highway Traffic Safety Institute.  The three tests are:

1. Horizontal Gaze Nystagmus (HGN)
2. Walk and Turn
3. One-leg stand

Horizontal Gaze Nystagmus is the involuntary jerking of the eye as it tracks a horizontal moving object (such as the tip of a pen or finger).   The officer will look for “lack of smooth pursuit” and “early onset of nystagmus prior to 45 degrees” to help determine if the driver is impaired. 

The Walk and Turn is a divided attention test where the driver is instructed to take nine heel-to-toe steps along an imaginary straight line, turn, and take nine heel-to-toe steps back.  The officer is looking to see if the driver starts the test early, can follow directions, keep his/her balance, leaves spaces between steps, steps off-line, uses arms for balance, etc.  If the driver does not perform this task as instructed the officer will form the opinion that you can not divide your attention between simple mental and physical exercises.

With the One-Leg Stand test the driver is instructed to stand with his/her heels together, arms at the side, raise one foot approximately six inches off the ground, and count out loud until the officer instructs you to stop.  The officer is looking to see if the driver uses arms for balance, sways in any direction, puts foot down, hops to maintain balance, body tremors, and muscle tension.

There are a couple additional FST’s the officer may use to help determine whether the driver is impaired by alcohol or drugs for purposes of driving.  These tests are:

1. Finger To Nose
2. The Rhomberg Balance Test
3. Recite the alphabet (do not sing the alphabet)
4. Touching the fingers to the thumb in a pattern described by the officer

In the Finger To Nose test, the officer instructs you to put your feet together, stand up straight with your eyes closed, and bring the index finger to the tip of the nose as you alternate hands.  The officer is looking for your ability to stand still without swaying, your ability to follow directions, eyelid tremors, etc.

With the Rhomberg Balance Test the driver is instructed to stand up straight with their feet together, tilt the head back, close your eyes, and estimate 30 seconds in your head.  When you believe you have reached 30 seconds you are to open your eyes and look straight ahead.  The officer is mainly testing your internal clock.  Your internal clock will be slow if you are under the influence of alcohol or depressants.

Although these tests are designed to determine if you are operating a vehicle while under the influence of alcohol or drugs, a person can perform poorly for many innocent reasons, including:  medical conditions that impair a person’s coordination, poor lighting, poor instructions, uneven pavement/street, and many other reasons.

Preliminary Alcohol Screening (PAS) Test:
Like other Field Sobriety Tests, a portable breath testing device is used in the field by the officer during the DUI investigation to determine whether the driver has a blood alcohol concentration above the legal limit.  What law enforcement officers don’t clearly tell you is that this test is voluntary; as are the FST’s outlined above.  You can politely decline to take the PAS test, but be aware that refusal to take the official blood or breathe test later (The Implied Consent Test) will be considered a refusal that carries with it enhanced penalties.