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Field Sobriety Tests

Drugged and drunk driving is a public health problem that states take seriously. Laws have evolved to encompass a wide range of dangerous driving to make roads safer. Police officers get specialized training to spot intoxicated driving. If a law enforcement officer stops you on suspicion of driving under the influence (DUI), you may have questions about what to expect.

Part of your encounter will involve determining if you are under the influence of alcohol or drugs. Police officers often use field sobriety tests to look for signs of intoxication.

Basics of Field Sobriety Tests

Field sobriety tests (FSTs), sometimes called roadside sobriety tests, help enforce DUI laws and usually precede chemical tests, such as Breathalyzer tests or other breath tests, as well as blood, saliva, and urine tests. All sobriety tests ensure that an officer has probable cause to arrest someone for driving under the influence.

A police officer typically performs three types of field sobriety tests during a traffic stop:

These tests allow an officer to observe your balance, physical ability, attention level, or other factors that the officer may use to determine whether you are driving under the influence of drugs or alcohol.

Officers will likely record your performance on field sobriety tests for evidence should you receive a DUI charge.

The Standardized Field Sobriety Test

The National Highway Traffic Safety Administration (NHTSA) endorses the Standardized Field Sobriety Test (SFST). Standardized tests are performed in the exact same manner every time to be accurate and admissible in court. To ensure this consistency, police officers undergo extensive training in performing FSTs.

Horizontal Gaze Nystagmus (HGN)

The term "horizontal gaze nystagmus" refers to the involuntary jerking of the eye that occurs naturally when the eye gazes to the side. This jerking, or nystagmus, becomes exaggerated when you are under the influence of alcohol. Officers look for three indicators of impairment in each eye:

  • Inability to follow a moving object smoothly
  • Distinct eye jerking when the eye is facing the farthest from center
  • Eye jerking when the eye is 45 degrees off-center

Walk and Turn (WAT)

This test aims to gauge your ability to complete tasks with divided attention. Most unimpaired people efficiently do this task. The police officer will direct you to take nine steps, heel-to-toe, along a straight line. Then, you turn on one foot and return in the same manner in the opposite direction.

One-Leg Stand (OLS)

The officer asks you to stand with one foot about 6 inches off the ground and count for 30 seconds. Swaying while balancing, using arms to balance, hopping, or putting the foot down indicates possible impairment.


Taken as a whole, the results of field sobriety tests accurately indicate alcohol impairment with a blood alcohol content (BAC) of 0.08% in 91% of all such cases. This level rose to 94% of cases if explanations for false positives were accepted, according to a 1998 study cited by the NHTSA. Suspects who fail FSTs are usually given a preliminary alcohol screening (PAS) to determine their blood alcohol concentration before an arrest. This may be a Breathalyzer or other breath tests.

Before performing FSTs during a traffic stop, the police officer should ask you about any medical conditions, disabilities, or injuries, as these can affect the accuracy of the tests. The officer will also consider your age, current medications, or other conditions in determining if FSTs are appropriate. For example, an inner ear condition or multiple sclerosis may make you unsteady, causing test failure.

Non-Standardized Field Sobriety Tests

Non-standardized field sobriety tests may include:

  • Standing with feet together and tipping the head backward
  • Counting the number of fingers an officer raises
  • Reciting the alphabet
  • Counting backward
  • Standing and leaning back to look up at the sky while holding arms to the side
  • Closing your eyes and touching your nose with a finger

Implied Consent Laws

All states have enacted implied consent laws. Under an implied consent law, law enforcement deems you to consent to chemical tests when you drive a motor vehicle. Chemical tests are more invasive than field sobriety tests, as they may require collecting a blood, urine, or saliva sample. While you may refuse to comply with chemical tests, you will face consequences for not cooperating. These vary by state but generally include immediate driver's license suspension, fines, or even a criminal charge.

Field sobriety tests differ, as refusing them will not bring additional penalties. However, refusal of FSTs or chemical tests will not prevent your arrest or keep you out of a police station. An officer can still arrest you on a DUI charge if they reasonably suspect intoxication.

Get a Better Understanding of Field Sobriety Tests by Speaking to a Criminal Defense Lawyer

Field sobriety tests are among several different techniques used by police to determine probable cause for a DUI arrest. If you performed FSTs as part of your DUI arrest, speak to an experienced DUI defense attorney. A criminal defense attorney in your area can evaluate your DUI case and provide you with valuable legal advice.

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