Authorities have many methods of determining a driver’s impairment level due to alcohol. Field sobriety tests are among the most commonly used. Failure to follow instructions or perform relatively simple tasks indicates that you may be under the influence and should not be driving. 

There are many field sobriety tests available for law enforcement to use, but only three have proved scientifically effective. Have you ever wondered what it takes to pass these tests or what the criteria are for failure? Learn what authorities look for specifically when administering standard field sobriety tests. 

One-leg stand test 

This assessment requires you to stand on one foot for 30 seconds with the other extended approximately six inches above the ground while you count by ones starting with 1,000. Putting your foot down before instructed can cause you to fail the test. Authorities may also penalize you for swaying, hopping or extending your arms to maintain your balance. 

Walk-and-turn test 

During this test, you must take nine steps along a straight line in a heel-to-toe fashion, then turn around on one foot and take nine steps in the other direction, still walking heel to toe. Putting your arms out for balance can penalize you here as well, as can an incorrect number of steps or an improper turn. The law enforcement officer will pay attention to whether you step off the line, as well as how well you listen to the instructions. 

Follow-the-finger 

This test requires you to follow a moving object with your eyes as it travels from side to side. The officer administering the test is looking for a specific involuntary jerking pattern of the eyeball called horizontal gaze nystagmus. This is a twitching motion that you cannot control. Most people are not even aware of it when it happens. However, it becomes more pronounced when you have been drinking. 

By themselves, each of these tests has an accuracy rate between 65 and 80%. However, the accuracy increases to 90% when authorities administer all three tests in combination.