When a police officer pulls over a driver on suspicion of DUI, the officer will likely ask the driver to perform a number of field sobriety tests. Some of these tests involve the driver getting out of the car and either walking or assuming a posture. Officers use these tests to determine if the driver has ingested too much alcohol. While field sobriety tests may reveal possible inebriation, other factors may register false positives.
The AAA DUI Justice website explains how some of these sobriety tests work. An officer may ask a driver to perform a walk and turn test, in which the driver will take nine steps, with each step touching heel to toe. The driver must walk in a straight line. Once the driver has completed the initial walk, the driver is to turn around and walk back the same way.
Officers may ask drivers to perform a one leg stand test. A driver will stand with a foot six inches over the ground. The driver must orally count starting from one thousand until the officer tells the driver to stop and place the foot back on solid ground. This test may go on for 30 seconds. During this and the walk and turn test, the officer will look for signs that the driver suffers from inebriation, such as a lack of balance or a failure to follow instructions.
However, medical conditions may interfere with the ability of a driver to pass one of these tests. Older drivers might not keep their balance as well as younger motorists. People who suffered an injury can experience balance or posture issues. Disabilities like reduced hearing may make it hard for a driver to follow the oral instructions of a police officer.
Diseases can also interfere with the ability of someone to maintain balance or concentrate on tasks like counting while holding a leg up. The NIDCD website describes a number of disorders that interfere with the ability of someone to maintain balance. The vestibular system, a complex system in the inner ear, helps keep balance. Various disorders affect this system and can create dizziness and vertigo. Such a disorder may make it impossible to keep up a steady balance or hold up a leg for any amount of time.