Skip to main content


Search for an Attorney  

DUI Field Sobriety Tests

Driving under the influence (DUI) is against the law. Field sobriety tests are conducted when a police officer suspects that a driver is impaired. Officers are trained to conduct the Standardized Field Sobriety Tests, which are a series of three tests designed to determine whether a driver is impaired or intoxicated. Police officers may claim these tests are accurate but there are a lot of problems with these tests that can prejudice your case. Ask your defense lawyer for advice after a drunk driving arrest.

Standardized Field Sobriety Tests

There are lots of indicators of impairment, beginning with how the suspect was driving. During a traffic stop, the law enforcement officer may be looking for other signs the driver is under the influence of alcohol, including slurred speech or the odor of alcohol.

If the officer suspects the driver may be impaired, they may ask the driver to perform some tests. This testing is intended to help the officer gather evidence to use to get probable cause to make an arrest. The National Highway Traffic Safety Administration (NHTSA) has provided the following information regarding each of the three standardized field sobriety tests (SFSTs):

  • One-Leg-Stand
  • Walk-and-Turn
  • Horizontal Gaze Nystagmus (HGN)

Horizontal Gaze Nystagmus Test

The eyes can make involuntary movements that you may not notice but someone watching your eyes can see. This involuntary movement is known as “nystagmus." The eyes may move rapidly when they move from side to side and up and down. The angle of the eye where nystagmus occurs can change after the driver's blood alcohol level gets to a certain point.

When the police tell you to follow their finger, a light, or pen back and forth, they are looking for the angle of onset of nystagmus and smooth pursuit. Failing the HGN test can be an indication that the driver may be impaired by alcohol. However, there are some problems with this test. Drivers have to rely on the police officer's estimation of angles and degrees. There are also some false positives that may change the HGN angle for sober people, including:

  • Infection
  • Medical conditions
  • Eyestrain
  • Prescription medications
  • Brain tumors
  • Inner ear diseases

Walk-and-Turn Test

The walk-and-turn and one-legged-stand are known as divided attention tests. These require the subject to concentrate on a mental and physical task at the same time. With the walk and turn, the subject is supposed to take 9 steps forward in a straight line, heel to toe, then turn and repeat. Drivers may not know that the “test" begins during the instruction phase. Indicators of possible impairment include:

  • Cannot keep balance during instructions
  • Starts too soon
  • Stops while walking
  • Does not touch heel-to-toe
  • Steps off the line
  • Uses arms to balance
  • Improper turn
  • Incorrect number of steps

There are problems with the reliability of this test. The officer may have given improper instructions, the road conditions may be dangerous, or even under ideal conditions, the subject could have a medical condition that makes it difficult to balance.


For the one-leg-stand-test, subjects are told to stand on one foot with the other approximately 6 inches off the ground and to begin counting up from 1,000 out loud. They are to continue counting until they are told to put their foot down, usually for about 30 seconds. The testing officer looks for four possible impairment indicators:

  • Difficulty balancing, leading to swaying
  • Using the arms for balance
  • Hopping on one foot for balance
  • Putting the foot down too early

Alcohol consumption and alcohol intoxication can cause a driver to fail the tests. But, like the other standardized field tests, there are reasons why a sober driver could fail the OLS test. False indicators may include:

  • Medical conditions
  • Age
  • Obesity
  • Difficult road conditions

Non-standardized Field Sobriety Tests

Some states have held that evidence obtained from field sobriety tests is inadmissible in court and can only be used to validate an arrest. As a result, drivers who are suspected of being impaired are sometimes subjected to non-standardized tests. These could include:

  • Standing with their feet together while moving their head backward
  • Counting the number of fingers shown by the officer
  • Counting backward from a prescribed number
  • Reciting the alphabet both forwards and backward
  • Leaning backward with their arms to the side and looking up at the sky
  • Placing their fingers on their nose with their eyes closed

Although these tests are not the standard, they can be equally incriminating, especially if they are recorded by a video camera in the officer's car. This type of footage is typically allowed as evidence in court.

Do I Have to Take the Roadside Tests?

It may not seem like you have an option but you have the right to refuse field sobriety testing. The officer may try and bait you by saying that if you're not drunk, you have no reason to refuse. However, there are reasons to refuse, even for sober individuals. There may be medical reasons or road conditions that could make you “fail" the test even if you were not drinking.

Some drunk drivers can “pass" the three-test battery. Passing the tests does not guarantee you won't be arrested. If you have questions about field sobriety test refusal and the sobriety test battery, talk to your criminal defense attorney.

What to Do After Failing a Field Sobriety Test

If you fail the field sobriety tests, the officer will generally place you under arrest and take you to the police station. During the booking process, the driver may have to provide a breath or blood sample for chemical testing. The chemical breath test is the most common way to test blood alcohol concentration (BAC). If the police suspect the driver may be under the influence of drugs, they may use a urine or blood test.

The results of the chemical testing can be used as evidence in the case against you, to show your blood alcohol content. In most states, the level of intoxication limit is 0.08% BAC. There may be increased penalties for higher BAC levels.

DUI Defense Attorney Legal Advice

There is still some question about the validity and admissibility of field sobriety tests and there are reasons other than alcohol impairment that could contribute to failing field testing. People who have been taken into custody as a result of their performance on field sobriety tests may find it helpful to consult with a DUI defense lawyer to find out the best course of action.