Field Sobriety Tests – what are they?
When people are stopped on suspicion of Driving While Intoxicated (DWI), officers might request that they complete a series of tests known as Field Sobriety Tests. These are a battery of tests developed by the National Highway Traffic Safety Administration (NHTSA) to determine whether a driver is impaired.
What kind of tests are they?
The standard Field Sobriety Tests developed by NHTSA include three physical tests and a Preliminary Breath Test (PBT). The three physical tests are the Horizontal Gaze Nystagmus Test, the Walk-and-Turn Test, and the One-Leg-Stand Test.
The Horizontal Gaze Nystagmus Test – This test involves the officer moving an object (a pen or a finger for example) in front of the driver’s eyes and having the driver follow the object. While this is going on, the officer is looking for a phenomenon in the eyes called nystagmus—nystagmus is the involuntary jerking of the eyes. The theory is that the presence of nystagmus, as indicated by certain “clues,” indicates an alcohol level of .08 or more. An example of a nystagmus test can be seen here.
The Walk-and-Turn Test – This test is what is called a “divided attention” test and is designed to observe a person’s ability to follow directions and perform a physical test. This test involves taking nine heel to toe steps, turning around 180° in a specific manner, and then walking back with nine heel to toe steps, counting each step out loud. The idea is that by dividing the driver’s attention between physical and mental tasks, the police can uncover a person’s “impairment.” This occurs by the officer looking for “clues” during the test such as not walking heel to toe, not counting out loud, starting the test to soon, doing an improper turn, using arms for balance, or taking the wrong number of steps. The presence of two clues (according to NHTSA guidelines) is a fail, indicating impairment. You can see an example of the walk-and-turn test here.
The One-Leg-Stand Test – This test involves the driver lifting one of their legs 6 to 8 inches off the ground and counting out loud by 1,000s until they get to 1,000-30. Again, the officer is looking for “clues” such as using their arms for balance, hopping, putting their foot down, not counting out loud, or swaying. Two clues (again, according to NHTSA guidelines) is a fail, indicating impairment. You can see an example of the one-leg-stand test here.
The last test that is typically administered to a driver suspected of impaired driving is the Preliminary Breath Test (PBT). This test is different from the three others in that it’s not testing physical ability, but rather it’s testing the person’s blood alcohol level (BAC). This test involves the driver blowing into a roadside machine which will give an approximate value of their BAC. Generally speaking, this test is not admissible in a DWI trial, but is only used to decide whether or not an arrest is warranted.
Do I have to perform the Field Sobriety Tests?
No, Minnesota law does not require you to perform the field sobriety tests, and your performance on those tests can and will be used against you later at a trial or hearing on your DWI case. Conversely, as noted above, (again, generally speaking), the PBT cannot be used against you at a trial and if you take that test, and are under the legal limit, you may not be arrested.
If you have questions about a DWI or field sobriety tests, please don’t hesitate to reach out to one of our experienced DWI attorneys!