Are Field Sobriety Tests Always Accurate?

Field sobriety tests are commonly used by law enforcement officers during DUI investigations to help assess whether a driver may be impaired. While these tests can provide officers with information during a roadside investigation, they are not perfect and may be influenced by a variety of factors unrelated to alcohol or drug impairment.

Understanding how field sobriety tests work—and their limitations—can help you better understand the role they may play in a California DUI case.

What Are Field Sobriety Tests?

Field sobriety tests are a series of physical and cognitive exercises that officers may ask drivers to perform during a DUI investigation.

The National Highway Traffic Safety Administration (NHTSA) has developed standardized field sobriety tests that are commonly used across the country.

These standardized tests generally include:

• Horizontal Gaze Nystagmus (eye movement test).
• Walk-and-Turn test.
• One-Leg Stand test.

Officers use these exercises as one factor in determining whether additional investigation may be appropriate.

Are Field Sobriety Tests Always Reliable?

No.

Although standardized field sobriety tests are widely used, they do not provide definitive proof that someone is under the influence.

Many factors unrelated to alcohol or drugs can affect a person's performance during these exercises.

Because every situation is different, field sobriety test results should be considered alongside the totality of the evidence in a case.

Factors That May Affect Performance

Several circumstances may make it more difficult for someone to successfully complete field sobriety tests, including:

• Uneven pavement.
• Poor weather conditions.
• Inadequate lighting.
• Heavy traffic nearby.
• Uncomfortable footwear.
• Fatigue.
• Anxiety or nervousness.

Even completely sober individuals may have difficulty performing the tests under challenging roadside conditions.

Medical Conditions May Play a Role

Certain health conditions may also affect a person's ability to complete field sobriety tests successfully.

Examples include:

• Back, knee, or ankle injuries.
• Balance disorders.
• Inner ear conditions.
• Neurological disorders.
• Vision problems.
• Physical disabilities.

These conditions may impact coordination or balance regardless of whether alcohol or drugs are involved.

Age and Physical Ability

Age and general physical condition can also influence performance.

Older adults, individuals with mobility limitations, or those recovering from recent injuries may naturally struggle with exercises that require balance, coordination, or precise movements.

These challenges do not necessarily indicate impairment.

Officer Observations Are Only One Part of the Investigation

Field sobriety tests are only one aspect of a DUI investigation.

Officers may also consider:

• Driving behavior.
• Physical appearance.
• Speech patterns.
• Odor of alcohol.
• Statements made during the encounter.
• Chemical test results, when applicable.

A DUI case is typically evaluated based on all of the available evidence rather than any single observation.

Reviewing the Administration of the Tests

How field sobriety tests are administered can also become an important issue in a DUI case.

An attorney may review whether:

• Standardized testing procedures were followed.
• Instructions were clearly provided.
• Roadside conditions affected performance.
• Body camera or dash camera footage supports the officer's observations.
• Other circumstances influenced the results.

Carefully examining these details may help identify issues that are relevant to the defense.

Every DUI Case Is Unique

No two DUI investigations are exactly alike.

The weight given to field sobriety tests depends on the specific facts of the case, the surrounding circumstances, and the totality of the evidence available.

A thorough review of all evidence is essential before evaluating any potential legal issues.



How the Law Offices of David A. Simon Can Help

At Law Offices of David A. Simon, we represent individuals facing DUI charges throughout San Diego and communities across California. We carefully examine every aspect of a DUI investigation, including the administration of field sobriety tests, police procedures, and the evidence gathered during the traffic stop. Our goal is to protect our clients' rights and provide experienced legal representation throughout every stage of the DUI process. Contact Law Offices of David A. Simon today to schedule a consultation.