Since the 1970s, law enforcement officers have been pulling people over and administering three roadside tests that help them gauge whether a driver is impaired. While these tests are not perfect, they do produce certain results that could lead to an arrest, a chemical test and a DUI charge on your record.
AAA describes the Standardized Field Sobriety Test and what an officer is looking for.
Horizontal gaze nystagmus test
When you have had too much to drink, and an officer asks you to track the side-to-side movement of a pen with your eyes only, your eyes will jerk rather than move smoothly. This indicates that your blood alcohol concentration is greater than 0.08 percent.
An officer is not just watching to see if you can keep your balance as you walk heel-to-toe in a straight line. He or she wants you to listen to the instructions before you begin and follow all of them without forgetting how many steps to take or how to properly make the turn. Putting out your arms or stepping off the line are other indicators that your BAC is too high.
One-leg stand test
Can you stand on one foot for 30 seconds while counting out loud? Most people with a BAC of 0.10 percent cannot. If you sway, hop, put your foot down or use your arms to maintain balance, the officer will suspect that you are intoxicated.
While these tests may identify an impaired driver, they may seem to indicate that you have been drinking, even when you have not. Many factors may thwart your ability to complete any of these tasks. For example, medication could affect the results of all three, and so could eye problems, inner ear problems and other health conditions. The officer should ask you if you have any issues that would compromise the test outcomes. You may want to call an attorney if an officer arrests you after administering an SFST.