Once a police officer initiates a traffic stop, the law allows for a limited investigation. If the officer suspects you of driving under the influence, he or she might require you to participate in field sobriety tests. These tests supposedly establish probable cause to arrest you. Unfortunately, their reliability remains in question. An officer might express confidence in their use, but don’t be fooled. Challenging them becomes a top priority in your defense.
The reliability of standardized field sobriety tests comes into question on a routine basis. Even the three tests considered most reliable — the horizontal gaze nystagmus test, the walk-and-turn test and the one leg stand test — have flaws. The margin for error in these and other field sobriety tests remains far too high for them to adequately support a conviction for DUI.
What makes field sobriety tests unreliable?
Police officers must administer and grade these tests according to proven scientific methodology, which they get from an approved manual. In reality, many officers receive their training from other officers, and ultimately, the training resembles the old game of “telephone” in which the information given at the beginning becomes muddled at the end, if it even resembles the original information at all.
Circumstances during the administration of the tests also affect their validity, for example:
- Lack of baseline: In the majority of cases, the traffic stop serves as the first contact the police officer has with you. He or she can’t determine whether you would pass the tests under other conditions. Any number of physical conditions could prevent you from “passing” one or more field sobriety tests.
- Sloped testing area: In order to the walk and turn test to yield appropriate results it requires a flat surface. Any slope could affect your balance.
- Failure to understand the purpose of the test: If an officer doesn’t know why the test works, he or she might not administer it appropriately.
- Quick, complex instructions: Rushing through the instructions could confuse you. In addition, conducting the test might not present a problem, but instructions often make it seem more difficult. If you fail to perform the test as designed, you could fail it.
- Injuries or handicaps: Either could affect your ability to perform the tests.
- Nervous conditions: Being nervous could cause you to fail the tests. Nervousness can even affect how you perform on the HGN test.
- The HGN Test and Vision Problems: Some diseases, contact lenses and other vision problems might cause false results to this test.
- Disease or illness: Either could affect your balance and coordination, among other things.
- Age: As you age, your coordination and balance could suffer, which means you might fail a field sobriety test.
- Lack of coordination: False test results could occur if you naturally suffer from balance and coordination issues.
As you can see, too many variables exist that could cause you to fail these tests. When you prepare your defense, a thorough review of the circumstances under which you performed the tests could reveal one or more issues with the results. Of course, other aspects of the traffic stop and your arrest require scrutiny. Your rights allow you the opportunity to review any evidence prosecutors intend to present to the court, and you should take advantage of that right.
Another right you retain allows you to bring in a criminal defense attorney to advocate on your behalf. He or she will review your case and advise you regarding a course of action that provides you with the best outcome to the charges possible.