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Field Sobriety Tests

If police suspect you of driving while intoxicated, they will test you. One of the tests they may implement is the Field Sobriety Test. Unlike a chemical test, the Field Sobriety Test does not require any equipment. It can be challenged in court.

Field Sobriety Test in Austin DWI Cases

As an Austin DWI defense lawyer, I will work hard to defend your Driving While Intoxicated case. I will independently review any field sobriety tests that were taken to make sure that they were administered properly and that the results were accurately reported by the arresting officer. I will take your DWI case to trial if necessary to fight against a DWI conviction. I can also help you get your DWI case expunged when that's possible.


Field Sobriety Test Info Center


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What are Field Sobriety Test and How do they Work?

In Texas, if you are pulled over by a police officer and suspected of driving while intoxicated (DWI), the officer will likely administer several tests to determine is you are possibly intoxicated. These tests are known as field sobriety test. Although the officer may administer a variety of tests, only three tests are recommended by the National Highway Traffic Administration (NHTSA).

An officer must be properly trained and administer the test correctly or else the test results will lack scientific validity.


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Horizontal Gaze Nystagmus

Nystagmus is an involuntary jerking of the eye that occurs naturally as the eyes gaze from side to side. Under normal circumstances, nystagmus occurs when the eyes are rotated at high peripheral angles. However, when a person is impaired by alcohol, the jerking becomes more noticeable and may occur at lesser angles. Someone that is impaired by alcohol will also often have difficulty smoothly tracking a moving object.

To administer the HGN test, the officer will have the driver follow a slowly moving object such as a pen or small flashlight, horizontally with his or her eyes. While the eyes are tracking, the officer looks for three indicators of impairment in each eye (6 total clues):

  • If the eye cannot follow a moving object smoothly;
  • If jerking is distinct when the eye is at maximum deviation, and;
  • If the angle of onset of jerking is within 45 degrees of center.

Out of these six clues, only two are needed to indicate impairment and BAC over the legal limit for purposes of DWI in Texas.

Research by NHTSA indicates that when administered properly, it is 77% accurate.


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Walk-and-Turn

The Walk-and-Turn (WAT) test is a divided attention test that consists of two stages, an instruction stage and a walking stage. The instruction stage requires a subject to listen to instructions given by the officer, while being required to stand in a heel-to-toe position and keeping his or her hands to their side for a certain amount of time. At the conclusion of the instructions, the subject will then walk in a straight line for nine steps, maintaining heel-to-toe, turn and walk back in the same fashion, while counting aloud the entire time. 

The police officer will be looking for eight clues that indicate impairment:

  • Lack of balance while listening to instructions
  • Starts before the instructions are finished
  • Stops while walking
  • Does not touch heel-to-toe
  • Steps off the line
  • Uses arms to balance
  • Improper turn
  • Incorrect number of steps

Out of these eight clues, only two are needed to indicate impairment and BAC over the legal limit for purposes of DWI in Texas.

Research by NHTSA indicates that when administered properly, it is 65% accurate.


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One-Leg-Stand

The One-Leg-Stand (OLS) test is another divided attention field sobriety test. During the One-Leg-Stand test, the subject is instructed to stand on one leg with their arms at their side, while watching the raised foot and counting out loud to thirty or until they are asked to stop by the officer. The officer will instruct the driver that their foot should be approximately six inches off the ground with their toe pointed away.

The police officer will be looking for four clues that indicate impairment:

  • The subject sways while balancing
  • Uses arms for balance
  • Hopping
  • Puts foot down (prior to 30 seconds)

Out of these four clues, only two are needed to indicate impairment and a BAC over the legal limit for purposes of DWI in Texas.

Research by NHTSA indicates that when administered properly, it is 65% accurate.