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Field Sobriety Testing in Texas

Field Sobriety Tests (FST’s) are the roadside tests administered by the police officer in investigating whether you were operating your vehicle under the influence of alcohol. Field sobriety tests are specific tests and were developed and sponsored by the National Highway Traffic Safety Administration (NHTSA). The standardized field sobriety tests, if given in the prescribed manner in a standardized setting, generally demonstrate valid indicators or clues of a person’s impairment. When the tests are administered in the form required by the NHTSA and an officer observes these clues, it allows him to establish probable cause to believe a driver is impaired and arrest that person for DWI. Most of the time, the officer does not or can not correctly administer the Field Sobriety Testing. The following are the three standardized field sobriety tests that are approved by NHTSA:

Horizontal Gaze Nystagmus

In the performance of this test, the officer asks the suspect to follow a pen or small flashlight, tracking left to right with his eyes. A person’s involuntary eyeball jerking (nystagmus) is magnified by the amount of impairment due to alcohol. There is a study that indicates that the tests, when done properly in a controlled environment, have an accuracy of 77% in identifying intoxicated drivers. Police officers conducting tests roadside regularly utilize this test in the formation of probable cause to place a suspect under arrest for DWI. Most officers do not accurately follow NHTSA training in performing these tests which mean that they are invalid.

Walk and Turn

The walk and turn test is a two-part examination. The first part is the instruction phase. The officer conducts observations of the driver during the course of the instruction phase of this test. During this time, the officer is verbally instructing and physically demonstrating how he wishes this test to be performed. The driver is told to stand still, feet together, and hands at his sides during the instruction phase. He is also instructed not to start the test until all of the instruction and demonstration phases are complete. The second phase is the performance of the test. What is required in the physical performance of the test is that the subject walk on a straight line, one foot in front of the other, touching heel to toe, keeping his arms to his side, counting the steps out loud. The subject is required to take nine steps out, turn and take nine steps back in the same manner. During the performance of this test the officer is watching for eight clues of impairment:

1. Loses balance during instruction
2. Starts test before instructions are finished
3. Stops during performance of test to steady self
4. Fails to touch heel to toe
5. Steps off of line
6. Uses arms for balance
7. Loses balance or turns improperly
8. Takes the wrong number of steps

If a suspect demonstrates two of these eight clues at any time during the performance of this test, the subject is deemed to have failed this test. There is a study that indicates that the tests, when done properly in a controlled environment, demonstrate a 68% probability that the subject is under the influence of alcohol and has a BAC of .10 or more.

One Leg Stand

Like the walk and turn test, the one leg stand also is a two-part test: instruction and performance. During the instruction stage, the suspect is required to stand with his feet together and his arms at his side. The officer will verbally instruct and demonstrate the performance of this test for the subject. The performance part of this test requires that the subject stand with one foot of their choice approximately 6 inches off the ground, straight out in front of them and count out loud by thousands for 30 seconds. The suspect is advised not to hop on the one foot or to use his arms for balance. During this test, the officer is trained to look for four clues of impairment:

1. Swaying while balancing
2. Using arms for balance
3. Hopping to maintain balance
4. Putting foot down before completion of test

If an officer observes two or more of the above clues the subject is deemed to have failed this test. There is a study that indicates that the tests, when done properly in a controlled environment, demonstrate a 65% probability that the subject has a blood alcohol content of .10 or more.


There are numerous conditions under which the tests should be administered as required by the NHTSA but are not always followed by the arresting officer. The tests are to be administered on a hard, dry, clean, non-slippery surface in a well-lighted area. Tests that are administered in less than standardized conditions diminish the results that an officer might obtain. These tests mentioned above are the only tests that are scientifically validated for use by an officer in detecting intoxication in a driver. Oftentimes, you will see or hear about tests such as touching finger to nose, picking up coins, and counting backwards being utilized by officers as field sobriety tests. There is no scientific validation for these tests and their reliability to accurately detect impairment is questionable. Remember, if any element of the standardized field sobriety test is altered or compromised, then the validity and reliability of the tests is compromised. The compromises can work in your favor.

In Texas, a driver has a right to refuse to perform field sobriety tests. By performing field sobriety tests, you are providing evidence to the officer in forming his DWI case against you. A driver is advised to exercise their right to refuse the performance of field sobriety tests. In the typical administration of field sobriety tests, a police officer will not describe to the subject the criteria he is looking for in the performance of this test, nor will he describe the number of clues necessary for the driver to fail the test. In a typical stop, the officer will ask the driver to perform several field sobriety tests. At the conclusion of those tests, the officer will simply inform the driver that he is placing the subject under arrest without any investigation or discussion with the driver about any deficiencies observed during the performance of the tests. It is the officer’s subjective determination that you failed the test that gives him probable cause to arrest you. Often the in-car-video does not support what the officer alleges.

Remember, everything you say and everything you do can and will be used against you in a court of law. Be smart and protect yourself.


This article is intended as an overview of basic field sobriety tests administered by local police departments as instructed by the NHTSA. The foregoing is provided for information purposes only.