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Challenging the DUI Field Sobriety Tests


If the defendant refuses to provide a chemical sample, prosecutors use the field sobriety tests to prove intoxication in court. If the defendant provides a sample, the three approved FSTs constitute evidence of probable cause. Either way, the FSTs are one of the most critical bits of evidence in a DUI prosecution.

To bolster this evidence, police officers often ask defendants to perform unapproved tests, such as the reciting-the-ABCs test. This tactic usually backfires. The judge often rules these test results are inadmissible. If that doesn’t happen, many jurors believe that prosecutors who use unapproved tests want to railroad the defendant.

If the probable cause evidence is weak, a Tampa DUI attorney has an excellent chance to successfully resolve a DUI case. This successful resolution could be a complete dismissal of charges, a plea to a lesser-included offense, or a not-guilty verdict at trial.

Horizontal Gaze Nystagmus

The follow-my-finger DUI eye test is based on involuntary pupil movements at certain angles. If the defendant shows more than a certain number of clues, the defendant probably has nystagmus.

That much is fairly certain, although roadside HGN tests aren’t conducted under controlled conditions. More importantly to a Tampa criminal defense lawyer, the connection between alcohol intoxication and nystagmus is very tenuous.

A childhood brain injury, not alcohol intoxication, is the leading cause of nystagmus. Many people have HGN, but the symptoms are so mild they only appear in very stressful situations, such as DUI arrests. In other words, these people couldn’t pass an HGN test whether they were under the influence of alcohol or not.

One-Leg Stand

Since it has the highest compliance rate, officers usually administer the HGN test first. When officers administer the next two tests, they’re clearly looking for intoxication. So, the compliance rate is much lower.

As they do in the HGN test, during the OLS test, officers look for various clues of intoxication, such as:

  • Failure to follow directions (starting the test too early, lifting the wrong leg, and/or ending the test too soon),
  • Swaying,
  • Using hands and/or arms for balance, and
  • Moving the elevated leg.

This test has connection issues as well. It shows the defendant has cognition and/or balance issues. But it doesn’t prove these problems were related to intoxication or fatigue, anxiety, or something else.


This test has connection issues as well. Furthermore, most people can only successfully complete the walking-a-straight-line test if they walk an actual line, as opposed to an imaginary line, in athletic shoes, as opposed to dress shoes, flip flops, or cowboy boots.

We mentioned fatigue and test results above. Officers usually administer the WAT test last. By this time, defendants are physically and mentally fatigued, especially if officers forced them to waste energy on unapproved tests. This fatigue skews the results.

Because of these uncertainties, many Hillsborough County judges only allow prosecutors to use FST results, especially HGN test results, in limited situations.

 Rely on a Dedicated Hillsborough County Attorney

A criminal charge is not the same thing as a criminal conviction. For a free consultation with an experienced criminal defense lawyer in Tampa, contact the OA Law Firm. Virtual, home, and jail visits are available.


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