Law officers use FSTs, or field sobriety tests, to help estimate the blood alcohol content of a suspected drunk driver. Three tests have been approved by the National Highway Traffic Safety Administration: the horizontal gaze nystagmus, the walk-and-turn test and the one-leg stand. If you are arrested for driving under the influence of alcohol, the prosecutor will use the results of these tests as evidence against you in court. However, there are various health issues that might affect the outcome of FSTs, making them an inaccurate indicator of a BAC level.
Medications and the HGN test
The horizontal gaze nystagmus refers to an involuntary jerking of the eyeball when you look to the side. If you are impaired by alcohol, the jerking motion may be exaggerated. You might also have trouble tracking a moving object, such as a pen or flashlight. Although the HGN test can indicate a BAC level of at least 0.08 percent, the intoxication threshold, asthma inhalants, seizure medications or a variety of depressants can affect the outcome of the test. Someone who has an eye disease and cannot see clearly obviously might fail the test.
Passing the walk-and-turn test
In this test, you're asked to take nine steps along a straight line, walking heel to toe. You then turn on one foot and repeat the walking maneuver in the opposite direction. The officer observing you will judge you on eight indicators, including losing your balance while listening to the instructions, using your arms for balance, stopping to regain your balance and stepping off the line. You might not pass this test if, for example, you have mobility issues or if you are an elderly person who becomes easily agitated or confused.
Balancing and the one-leg stand
If you have taken yoga classes, you are probably familiar with the one-leg stand and you may be good at it. However, as part of a field sobriety test, you will be asked to stand on one foot and count aloud by ones, beginning with one thousand, until you are given permission to put your foot down. You will be timed for thirty seconds and the BAC indicators the examiner will look for include swaying, using your arms or hopping to maintain your balance or putting your foot down before time's up. Once again, medical issues may come to the fore. You may have an injury that prevents you from balancing properly on one foot, or you may be subject to dizziness or vertigo, which makes balancing in any form almost impossible.
Protecting your rights
There are many health issues that may prevent someone from completing a field sobriety test successfully. If you failed an FST due to a medical problem and are uncertain how to proceed, an experienced DUI defense attorney can step in to help you and better protect your rights.