If you are pulled over for suspicion of driving under the influence of alcohol in the Ann Arbor/Ypsilanti area, the police officer will likely request that you perform a variety of standardized field sobriety tests to establish probable cause to arrest you for drunk driving. So, just how accurate are standardized field sobriety tests results in determining intoxication? Read each test description below to find out.
1. The Walk-and-Turn Test
When conducting the walk-and-turn test, the police officer will instruct you to walk nine steps in a heel-to-toe fashion in a straight line. After you take the ninth step, you will have to turn around on one foot and return in the opposite direction in a heel-to-toe fashion for another nine steps.
During your test performance, an officer will look for 8 indicators of impairment: 1) Did you stay balanced while listening to the officer’s instructions; 2) Did you begin the test prior to the officer telling you to start; 3) Did you have to stop while walking to regain your balance; 4) Did you touch heel-to-toe; 4) Did you step off the line; 5) Did you have to use your arms to balance; 6) Did you make an improper turn; and/or 7) Did you take an improper amount of steps?
If you exhibit 2 or more of the 8 indicators, this indicates to the officer that your blood alcohol content (BAC) may be above the .08% legal limit.
According to National Highway Traffic Safety Administration sponsored research in 1998, this test has a 79% reliability reading factor that a driver is impaired (BAC of .08% or higher) if the officer administers the test correctly. Research in 1981 found a 68% reliability reading factor that a driver’s BAC is .10% or higher if the officer administers the test correctly.
2. One-Leg Stand Test
For the one-leg stand test, the police officer will ask you to stand with one foot approximately six inches off the ground with your foot parallel to the ground. You must maintain your balance while you count to a designated number.
During your test performance, an officer will look for 4 indicators of impairment:1) Did you sway while trying to balance on one-leg; 2) Did you use your arms to balance; 3) Did your feet touch the ground while you were standing on one leg; and 4) Did you hop to maintain your balance?
If you exhibit 2 or more of the 8 indicators, this may indicate to the officer that your blood alcohol content (BAC) is above the .08% legal limit.
According to 1981 researchers, this test has a 65% reliability reading factor that a driver is impaired (blood alcohol content of .10% or higher) if the officer properly administers the test and the driver unsuccessfully performs this test. The 1998 research found an 83% reliability reading factor that a driver is impaired (BAC of .08% or higher if the officer correctly administers the test and the driver unsuccessfully performs the test.
3. The Horizontal Gaze Nystagmus Test
Nystagmus is the technical term for involuntary jerking of the eyeball. When administering the horizontal gaze nystagmus (HGN) test, the police officer will ask you to look at a pen, pen light, or their finger as they move it from one side to another while observing your eye movements. If there is a jerking movement in your eye before your gaze reaches a 45-degree angle, then this will indicate a possible BAC level over .08%.
According to 1981 researchers, this test is reliable 77% of the time for indicating that a driver is impaired (blood alcohol content of .10% or higher) if the officer correctly administers this test and the driver unsuccessfully performs the test. The 1998 research found the HGN to be 88% accurate in indicating that a driver’s BAC is .08% or higher if the officer correctly administers the test and the driver unsuccessfully performs the test.
Further, according to the 1981 research, the three standardized field sobriety tests combined were 81% correct in estimating a BAC of .10% or higher when administered correctly. The 1998 study found even greater accuracy for all three tests indicating a BAC of .08% or higher when administered correctly
How to Challenge Standardized Field Sobriety Test Results
Though studies suggest that officers can usually determine if a person is intoxicated based on the standardized field sobriety test results, there are instances when such results are not accurate due to several factors.
Standardized field sobriety tests must be administered in specific conditions in order for the results to be disclosed in court during a trial as evidence of the defendant’s impairment or intoxication. For example, if the one-leg stand test was administered on a severely un-leveled sidewalk, this may impact your test results. The same is true if the officer fails to administer the tests correctly.
Contact Washtenaw County drunk driving attorney Stacey Washington for a case evaluation if you have been charged with a DUI.