DUI – Understanding Standardized Field Sobriety Tests

When you have been pulled over on suspicion of driving under the influence (DUI), the officer has several tools at his or her disposal for determining your estimated level of impairment. The officer will observe your posture, speech patterns, and overall demeanor, looking for indications that you have had too much to drink. You may also be asked to take a preliminary breath test—one that is not necessarily admissible in a criminal trial, but a test that can still be used against you at your license suspension hearing.

Prior to being arrested, it is also likely that the officer will ask you to participate in a series of assessments known as the standardized field sobriety tests or SFSTs. It is important to know that you are permitted to refuse all standardized field sobriety tests and you are also able to refuse any request by the officer to take a breath test, whether it be a portable breath test or the “official” test at the police station after your arrest.

What Are SFSTs?

The standardized field sobriety tests are a battery of three separate tests approved by the National Highway Traffic Safety Administration that help law enforcement determine a driver’s level of impairment in a potential DUI situation. The tests allow the officer to observe and note involuntary movements and reflexes, as well as the driver’s ability to follow directions and complete simple physical tasks. Each test has a number of “indicators” that help the officer decide whether the driver is likely to be impaired. The tests are not foolproof, but they are backed by scientific research and accepted as rebuttable evidence in a DUI prosecution.

The three standardized field sobriety tests include:

  • Horizontal gaze nystagmus (HGN): When conducting the HGN, the officer asks the driver to follow a stimulus—like a pen or a raised finger—with only his or her eyes. The officer moves the stimulus from side to side while watching the driver’s eyes for involuntary jerking called nystagmus. While nystagmus occurs for sober individuals as the eyes reach a certain horizontal angle, it usually starts sooner and is more pronounced when a person is impaired by alcohol or drugs;
  • The walk-and-turn: The walk-and-turn is the test that most people think of when they hear the term “field sobriety test.” During this test, the driver must take nine steps—heel to toe—along a painted or imaginary line, pivot 180 degrees, and walk back nine steps. While the driver walks and counts the steps aloud, the officer looks for trouble balancing, swaying, and a lack of coordination as the driver turns. Starting too soon and losing count are also indicators of impairment;
  • The one-leg stand: The third test requires the driver to stand with one leg raised so that one foot is parallel to and about six inches off the ground in front of the body. The driver must look at his raised foot while counting slowly. In most cases, the test will last about 30 seconds while the officer watches for hopping, swaying, or the driver putting the foot down.

Individually, the SFSTs are accurate in predicting a driver’s level impairment about 60 to 70 percent of the time. Taken as a whole, however, they are much more convincing. A sober driver, for example, with weight issues or middle ear problems, may fail the one-leg stand test due to his or her physical limitations, but pass the HGN.

Contact Us Now

It is important to realize, however, that SFSTs are not infallible. If you have been arrested and charged with DUI, contact an experienced Joliet criminal defense lawyer to explore your options. Attorney Jack L. Zaremba is a former Will County prosecutor who understands how to challenge field sobriety tests and other evidence collecting methods used by law enforcement. Call 815-740-4025 for a free consultation today.

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