A guide to field sobriety tests

When assessing a person before a potential drunk driving arrest, officers may use three standardized field sobriety tests.

Iowa residents who are facing charges for suspected drunk driving will want to understand exactly how the state approaches these situations. A drunk driving arrest process many involve many steps including the administration of field sobriety tests. It is important, however, for people to know that it is not these tests that are used to determine an exact level of intoxication.

It is only a chemical test that can identify how much, if any, alcohol a person actually has in their system. A chemical test may be conducted on samples of breath, blood or urine. An alcohol reading of 0.08 percent or greater is considered legally intoxicated.

Just what are field sobriety tests for then? As FieldSobrietyTests.org explains, these tests are designed to give law enforcement officers enough evidence with which to justify an arrest for operating of a motor vehicle while intoxicated.

Are field sobriety tests accurate?

Of the three tests that the National Highway Traffic Safety Administration has sanctioned for use in a drunk driving investigation, the accuracy rates of each test individually range from a low of 65 percent to a high of 77 percent. When used together, the accuracy of all three tests is said to be only 82 percent.

What are the three tests sanctioned by the NHTSA?

One of the field sobriety tests is called the horizontal gaze nystagmus test. A nystagmus is a twitching of the eye that people cannot control. It is said to be more pronounced if a person has consumed alcohol. The greater the level of this twitch an officer sees, the more likely it may be that a person can be deemed as having failed this test. There are specific things that an officer looks for in the eye when tracking its motion with a light that determine a failure or passing of this test. This test's accuracy rate is 77 percent.

Another test is the walk-and-turn. In this test, a person is required to walk in a straight line with arms kept firmly at their sides. Feet must move in a strict heel-to-toe fashion. Also, the person must count so that the officer can hear them while walking. Nine steps are required in one direction and nine steps are required back to the starting point. Things like moving one's arms in an attempt to balance may contribute to a failure of this test. This test's accuracy rate is 66 percent.

The final test is the one-legged stand test. Its accuracy rate is lowest of all at 65 percent. A driver is required to balance perfectly on one foot with no use of arms for balance. Again, multitasking ability is reviewed as the person must count out loud at the same time. Road condition, shoes, medical conditions and nervousness may all make it difficult for a person to pass this test.

How can a driver get help after an arrest?

If an officer deems a person to have failed these tests, it may be helpful for a lawyer to review the notes from the arrest to ensure that all of the tests were properly administered. Iowa residents should always reach out to an attorney after an OWI arrest to learn about this and other options for their defense.