Field Sobriety Tests

As DUI lawyers who regularly meet people that have been asked to perform field sobriety tests, we rarely meet someone who truly understands these tests.

Standardized Field Sobriety Tests or "SFST" for short, are used by police officers all over Washington, and the entire US, when they are screening motorists who have been detained for suspicion of driving under the influence (DUI). The Standardized Field Sobriety Tests were developed as a result of research commissioned by the National Highway Traffic Safety Administration (NHTSA) in the 1970s.

NHTSA is a sub agency of the Federal Department of Transportation (DOT) and assists states and local communities in attempting to reduce the threat of drunk driving. The DOT conducts research on driver behavior and traffic safety, to develop the most efficient and effective means of bringing about safety improvements. In the course of this, they have funded studies on field sobriety tests and the training of law enforcement officers in the administration of the standardized field sobriety test battery.

The NHTSA and police agencies believe that there is a correlation between an individual's performance on the physical coordination tests and their ability to drive. They usually will ask a motorist detained for DUI to perform a battery of three tests, which include the walk and turn; one leg stand; and horizontal gaze nystagmus (HGN) tests.

The HGN test is one where an examiner holds a stylus or object, often a pen, in front of a test subject and records the results of their performance while moving their eyes in a horizontal and vertical manner as directed by the officer. If the person displays nystagmus in the correct portions of the test, they will be considered to have "clues", and enough clues will mean that essentially the person fails the test. Unfortunately, nystagmus is not something that the affected person can observe, and it is too subtle to be observed by a patrol car's camera or a police officer's body camera. This means that the only person who could observe it is the police officer.

The walk and turn and one leg stand tests are designed to test a person's ability to follow directions, as well as their physical coordination. Most subjects fail these tests, and they usually do not know how the test is graded or even when they fail.

The validity of the SFSTs hinges on standardized administration and scoring. To the extent that officers' instructions and demonstrations, or their interpretations of observations, differ from those established by research, it diminishes the meaning which can be attached to drivers' test performance.

As criminal defense attorneys, we must know more about field sobriety tests that the police officers that give them, in order to explain the shortfalls or errors in how our clients are tested by law enforcement, in addition to the flaws in the tests themselves. At times we will retain the services of experts in these fields, in order to better explain these difficult concepts to juries and judges.

My advice to anyone who is pulled over for any reason, and asked to take field sobriety tests, is to respectfully decline to take them, and ask to speak with a criminal defense lawyer prior to making any further statements. Field sobriety tests are voluntary, and the reason that law enforcement is asking a suspected motorist to take them is to gather evidence of driving under the influence. By refusing to participate in these tests, motorists are simply exercising their right to decline to make statements that might incriminate them.

There is one additional test that some consider a field sobriety test, and that is what we call a PBT or preliminary breath test. It is a breath test device that is portable and about the size of a deck of cards. It is a lower quality breath test than the evidentiary one used at the police station or jail. I recommend that those asked to take this test decline to do so, as there is no requirement that anyone take it. People sometimes mistakenly think that a failure to take the PBT will result in a license suspension or other penalty, however they are confusing the PBT with the evidentiary breath test given at the police station or jail, for which there can be additional penalties for failure to perform.