Field Sobriety Tests

Field sobriety tests are standardized physical tests used by law enforcement officers to determine if a driver is impaired and to determine if there is probable cause to support a driver’s arrest for DUI.  Field sobriety tests have been utilized for decades and were utilized prior to the availability of chemical tests such as blood tests and breathalyzers. 


Fresno DUI Attorney, Michael E. Mitchell, has received certification for his completion of both the field sobriety practitioner as well as the field sobriety instructor courses.  Mr. Mitchell’s instructors, Robert La Pier and Anthony Palacios, were instructors for the Idaho and Georgia State Trooper respectively.

While many officers conduct field sobriety tests as part of a driving under the influence investigation, many officers have not been trained to adequately administer the tests. Many of the field sobriety tests that police use are not standardized or scientifically validated in any manner.


The key ingredient that makes standardized field sobriety tests reliable is the fact that the officer does the tests in a standardized manner.  The clues and other observations that the officers' note in their police reports can be used to demonstrate that the officer did not know how to adequately perform the tests. This can lead to either a determination that there was inadequate probable cause to support the arrest or it can be used to show that you were not under the influence at the time of driving.  Doubt about the reliability of the chemical test combined with inadequate field sobriety tests can lead to the case being reduced or a not guilty verdict.  

Were the tests Scientifically Validated?

The standardized field sobriety tests that are scientifically validated include the following tests:

  • Horizontal Gaze Nystagmus (following a stimulus, such as a finger or pen with your eyes)
  • Walk and Turn
  • One Leg Stand

The field sobriety tests that are non-standardized include the following tests:

  • Rhomberg test (Modified Position of Attention Test)
  • Finger Count
  • Hand Pat
  • Reciting your ABC’s
  • Finger to Nose

It is not uncommon for us to see officers mix and match different criteria from field sobriety tests. 
In addition, we often see officers fail to demonstrate a proficient knowledge of how to perform the tests when they are on the witness stand.  There are also scientific studies, such as the 1994 study from the Clemson University which demonstrate that these tests are highly unreliable. 

Use our Knowledge to Attack your DUI Charge

In the Clemson study, 14 officers were asked to rate the performance of 21 individuals after watching them on videotape.  Even though all 21 individuals had 0% alcohol in their system, the fourteen officers found that only three of the individuals appeared to be “unimpaired” based upon their field sobriety test performance.  Studies such as this can have a devastating impact when used on cross-examination.   Knowledge is power and putting our knowledge on your side gives you the best chance to avoid a DUI conviction.  Call the Mitchell Law Group today to arrange a free evaluation of the field sobriety tests and other aspects of your DUI case today.