Standardized Field Sobriety Tests - California DUI Law and Legal Information

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  8.  » Horizontal Gaze Nystagmus
  9.  » Walk and Turn Test
  10.  » One-Leg Stand Test
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When California law enforcement officers including members of the California Highway Patrol (CHP), local police officers, or sheriff's deputies suspect a motorist of driving under the influence (DUI), they will usually ask the driver to perform so-called field sobriety tests (FST's). These are frequently conducted next to a busy street or freeway filled with distracting sights and sounds. Additionally, most field sobriety tests are unreliable and are not accurate predictors of whether a person was driving under the influence or driving with a blood alcohol level of 0.08% or greater.

Nonetheless, the driver's performance on the field sobriety tests are used by law enforcement officers as probable cause to require a person to provide a breath sample into a preliminary alcohol screening (PAS) device and to arrest a person for DUI. Additionally, the police officer CHP officer will attempt to use a driver's performance on field sobriety tests as evidence of driving under the influence in a DUI trial or DMV hearing.

The experienced San Francisco DUI attorneys at the Law Office of Robert Tayac will challenge the validity of the field sobriety tests at the criminal trial and the Department of Motor Vehicles (DMV) hearing. The Law Office of Robert Tayac is an experienced firm of attorneys specializing in DUI defense. We invite you to contact the office to schedule an appointment to consult with a DUI lawyer at our San Francisco office.

The National Highway Transportation Safety Administration (NHSTA) has recognized three standardized field sobriety tests - the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test. Because these three tests have been endorsed by the NHSTA, they carry more weight in court than non-standardized tests, but a skilled California DUI defense lawyer can successfully challenge the results of field sobriety tests in court.

Although field sobriety tests are designed to measure mental and physical impairment from alcohol use, they are inherently flawed in one important way. Many of the so-called signs and symptoms of alcohol impairment stem from physical problems that are unrelated to alcohol intoxication.

In order to find a motorist guilty of Driving Under the Influence (DUI), or Driving While Intoxicated (DWI), a jury must be convinced of the driver's guilt beyond a reasonable doubt. Field sobriety tests reliance on physical impairment creates problems for prosecutors, and creates doubt in the minds of jurors. An experienced California DUI defense attorney will use that fact to the client's advantage.

This aspect of DUI defense is of importance when facing a charge of drunk-driving. Experts agree that when it comes to alcohol intoxication, mental impairment always occurs before physical impairment. Physical impairment can be masked by those with a high tolerance to alcohol, but mental impairment can never be masked. If a driver is physically impaired but not mentally impaired, the physical impairment must stem from a source other than alcohol, and a jury must acquit a driver on a charge of driving while impaired.

Many conditions other than alcohol intoxication can cause a driver to show signs of physical impairment, including fatigue, injury, illness, or nervousness. A criminal defense lawyer with experience defending California DUI cases can determine whether causes other than alcohol may have contributed to any impairment, and challenge the results of any field sobriety test.