DUI Roadblocks: Field Sobriety Tests


Almost everyone is familiar with some level of the standard “Field Sobriety Test,” or FST’s.  They are performed at almost every DUI stop, and the consequences of not understanding what law enforcement is looking for in these tests could result in increased scrutiny and suspicion.


The California Highway Patrol Manual says FST’s are designed to evaluate a person’s ability to divide his/her attention. FST’s require you to concentrate on several things at once. In order to drive a car safely, a driver must also concentrate on several things at once: react appropriately to a constantly changing environment while simultaneously controlling steering, acceleration, and braking. Alcohol and other drugs reduce a person’s ability to divide attention. Even when under the influence of alcohol, people can handle a single focused attention task fairly well. For example, a driver may be able to keep her car within the lane as long as the road is straight when the road curves; the impaired driver may not and run off the road.

Field sobriety tests require a person to demonstrate at least two or more physical and or mental skills simultaneously. Prosecutors and law enforcement insist FSTs are simple and an average person should have no difficulty performing the tests when sober. However, this is not true.  Most of the tests are extremely foreign to those who have been pulled over for DUI, and it is likely this is the first time they have ever performed these requested tasks in their lifetime!

In a scientific article published in 1994, “Field Sobriety Tests: Are They Designed for Failure?” authors Spurgeon Cole and Ronald H, Nowaczyk sum up the problem:

“The fact that these tests are largely unfamiliar to most people and not well practiced may make it difficult to perform them.”

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