If police officers stop you on suspicion of DUI or DWI, they may ask you to take a field sobriety test. Unfortunately, failing this test can mean an immediate arrest, with the resulting damage to your record.
For several reasons, agreeing to take a sobriety test is more likely to harm than help you.
Remember: Missouri law does not obligate you to consent to this test, as implied consent only applies to chemical testing. Remaining polite while continuing to refuse the test is usually the best course of action.
How the test works
The Standard Field Sobriety Test consists of three parts: the one-leg stand, the horizontal gaze nystagmus test and the walk and turn. Perfectly sober people can fail any of these tests for several reasons.
The directions are also a test
The first part of the test actually consists of the directions. Police officers instruct you precisely how to perform the actions involved in the test and may perceive mistakes as indicative of impairment. However, if all this takes place next to a busy road, you may simply mishear the instructions.
Most people tend to be very nervous in situations involving potential arrest; someone prone to anxiety may be even likelier to misunderstand instructions or fumble the tests.
Common reasons for failing
The one-leg stand tests your ability to perform a basic balancing task. However, while substance impairment can certainly affect your balance, so can many other factors.
Older people may have trouble with this test. A prior injury, an inner ear problem and any medical condition that tends to cause vertigo can cause someone to lose balance, as can an uneven road surface or uncomfortable footwear.
The horizontal gaze nystagmus test measures your ability to track movement and focus your eyes. While deficiencies in this area can signal impairment, they can also indicate many types of medical problems or intake of medications. The same is true for the walk and turn.
Test results are not objective
Further, whether you pass or fail a field sobriety test can depend heavily on the perceptions of the officer administering it. Even conscientious officers at the top of their game can have preconceptions that influence their understanding of what they see.