When law enforcement officers pull over drivers on suspicion of driving under the influence, they may ask them to perform a field sobriety test. This comprises three tests that test balance, coordination and other physical factors that may indicate intoxication.
However, these tests have a problem. They are highly unreliable, and various reasons can result in a positive even when an individual has not had a drop of alcohol or any other controlled substance.
1. Medical conditions
Certain medical conditions, such as inner ear problems, dizziness, stroke damage or neurological disorders, can have an effect on a person’s balance and coordination. Eye conditions can affect the outcome of the horizontal gaze nystagmus test, where officers ask drivers to follow an object with their eyes. Anxiety, or even just nervousness, can also affect individuals’ ability to perform the tasks.
2. Fatigue
Fatigue can also impair a person’s ability to perform field sobriety tests accurately. Lack of sleep can affect cognitive function and motor skills, as well as the appearance and behavior of the eyes.
3. Environmental factors
Environmental factors, such as uneven terrain or inclement weather, can make it more difficult for drivers to keep their balance or walk in a straight line, which are activities required to pass the tests. Poor lighting may also affect the carrying out of or judgment of the tests.
4. Error
Police officers can make errors while administering the tests. Because the results have a basis solely in their judgment, the tests are also subjective, making them susceptible to interpretation mistakes. One police officer who made many false DUI arrests arrested a person for having “tremors” in her eyes even though this individual did not drink or partake of any drugs.
Field sobriety tests are a common tool used by police officers. However, they are subject to several flaws and many factors can result in a false positive. Drivers have the right to refuse to take field sobriety tests. Any false positives can and are likely to end up as evidence against them.