Field Sobriety Test

What is a Field Sobriety Test?

Any time an officer suspects a crime of being committed the officer is expected to investigate and gather evidence, suspected DWI is no different. When an officer pulls a driver over that he or she believes has been drinking he will usually perform a series of tests designed to see if the driver is physically and or mentally impaired. These tests are not meant to determine guilt, instead they help officers establish probable cause to arrest.

Do I have to take the Standardized field tests?

In short, no. You may refuse to perform, or continue to perform, field sobriety tests at any time. While it is your right to refuse, refusal alone might not prevent the officer from arresting a suspect. The decision of whether or not to perform a Field Sobriety test is a complicated decision that is best made on a case by case basis.

How are Field Sobriety Tests performed?

While you may be familiar with some of the more well-known “tests” like saying the alphabet backwards or touching the tip of your nose with your index finger, there are actually only three Standardized Field Sobriety Tests recognized by the National Highway Traffic and Safety Administration (NHTSA). Unlike the others, these three tests, alone, have been found to indicate an intoxicated driver with reasonable accuracy. These tests are typically performed by officers who have been trained in how to perform them and taught the standardized “clues” as established by NHTSA. The tests are as follows:

The Horizontal Gaze Nystagmus Test: Or HGN for short, is a test that asks a suspect to follow the tip of a pen, flashlight, or fingertip with his or her eyes as the officer moves it from side to side in front of the suspect.

During the HGN test the officer watches the suspect’s eye movements looking primarily to see if the suspect has trouble focusing on a moving object and for any trembling of the eyes (nystagmus) rather than the usual smooth movements as the suspect watches the pen move.

While failure of this test could possibly be an indication that the suspect is intoxicated, there are a number of other factors that could give the officer a false positive. Lack of sleep, medical conditions effecting the eyes, and certain prescription medications are aa few things that may cause an otherwise sober person to show signs of Nystagmus. There are six total clues on the HGN test, three for each eye.

The Walk and Turn: This test, as its name suggests, involves a suspect taking a series of steps in a straight line, turning around, and walking back up the line. The officer will ask the suspect to take a number of “heel to toe” steps (nine is the NHSTA standardized number) before taking a series of small steps to turn around, and repeat the same number of heel to toe steps.

The Walk and Turn is a “divided-attention test.” In this test the officer is watching for two different things. First, the suspect’s ability to follow directions. Intoxicated people will usually have trouble taking the correct amount of steps, turning the way the officer showed them, or waiting until the instructions are finished to begin. Second, the officer looks for physical difficulties while performing the test, failing to walk in a straight line, stumbling/loss of balance, or an inability to do a heel to toe step are all clues that a suspect may be intoxicated.

Just like HGN, this test is not perfect and there are several circumstances that could cause a sober person to fail. Age, lack of sleep, and any type of physical injury, especially to the legs and back, could all prevent a sober person from passing this test. External factors like weather or road conditions can also play a huge role in causing an inaccurate result. An officer is looking for eight standardized clues in determining a person’s sobriety. Officers are looking for Two out of the Possible Eight clues to determine that a suspect has failed the test.

The One-Leg Stand: The final NHTSA certified test involves a suspect looking straight ahead, with arms at their side, and balancing on one leg with the other foot raised about six inches off the ground in front of them. The suspect is then instructed to count to 30 out loud while the officer watches.

Much like the Walk and Turn, the officer is looking for ability to follow instructions and any physical difficulties in performing the test. Counting to the wrong number, extending your arms more than six inches for balance, or putting your foot down before the officer instructs you to are all indicators that the suspect is intoxicated.

Again, as with Walk and Turn, factors like age and physical injury can cause an otherwise sober person to have difficulty performing this test. A trained officer will usually ask a suspect beforehand if he has any physical limitations that may impact his ability to perform the test.

An officer will most likely ask a suspect to perform all three of these tests, but under some circumstances an officer may choose only to administer one. Additionally, while these three are the only tests that have been found to be scientifically relevant, an officer may ask a suspect to perform other non-standard exercises (like saying the alphabet backwards or counting from a certain number to another number).

Failing a Field Sobriety Test

The most important thing to remember is that failure of one, or even all, of these tests does not make you guilty of DWI. As you read above, these tests are far from perfect and are not intended to prove someone was intoxicated beyond a reasonable doubt. These tests are merely one piece, in the complex field of DWI law, for your attorney and the courts to consider.