Field Sobriety Tests and a DUI Arrest

 Posted on December 30, 2014 in DUI and Breath Alcohol Tests

Field sobriety tests, or FSTs, are a critical part of a DUI arrest. If an officer suspects that a motorist may be intoxicated, the officer nearly always asks the driver to perform these agility tests. These tests also indicate whether or not a person is mentally impaired.

There are a number of FSTs, but only three have been approved by the National Highway Transportation Safety Administration. The arresting officers always say that the defendants failed the tests, and therefore they were arrested. By challenging the results, an attorney may be able to show that there was no probable cause for a DUI arrest and a case may be thrown out.

Horizontal Gaze Nystagmus

Most people are familiar with the HGN test. The test administrator, who is nearly always the officer, asks the subjects to follow a point with their eyes without moving their heads. The point is usually the tip of an ink pen in daylight hours and a flashlight at night. Nystagmus is an involuntary eye jerk. If there are four or more clues between the two eyes, the subject may have a BAC of at least .08.

There are some problems with this test. Most DUI arrests occur at night, and the patrol car’s flashing lights are just a few feet away. The test conditions are not controlled, and that could affect the outcome. Moreover, there are a variety of legal drugs which can cause nystagmus. Finally, according to NHTSA, the test is only 88 percent accurate, even in perfect conditions.

One Legged Stand

The OLS is primarily an agility test, but officers also are looking at the subject’s ability to follow directions. Some subjects may lift the wrong leg, hold the leg at the wrong angle or have it in the air for the wrong length of time.

The officer does not always provide the subject with a level place to stand, or give women the opportunity to remove high-heeled shoes. Uneven footing, along with the aforementioned flashing lights, can easily cause a person to lose balance.

Walk and Turn

In addition to agility, this test also measures a person’s ability to multitask, because the subject must simultaneously count the steps, walk in a straight line, and walk heel-to-toe.

Sometimes, the subject is asked to walk an imaginary line as opposed to an actual line, like a parking lot stripe or road stripe. It is almost impossible to complete this task if there is not fixed point of reference.

If a DUI arrest is invalidated, a case cannot move forward. For a free consultation with an experienced Arlington Heights DUI defense attorney, contact Scott F. Anderson. Your first visit is free.