Standardized field sobriety tests (“SFST”) are what the police use to try to determine if a person is intoxicated.  The only three SFSTs are as follows:

  • horizontal gaze nystagmus (HGN) test;
  • one-leg stand test; and
  • walk and turn test.

These three tests were developed by researchers funded by the National Highway and Traffic Safety Administration (NHTSA).  It is this research that the police and prosecutors use to try and prove that a person is intoxicated.

SFST’s are standardized because:

  • Tests are administered in the prescribed, standardized manner;
  • Standardized clues are used to assess the suspect’s performance;
  • Standardized criteria are employed to interpret that performance

If any one of the standardized filed sobriety test elements are changed, the validity is compromised.  See NHTSA DWI Detection and Standardized Field Sobriety Testing Manuel.

The fact that the tests are standardized makes it essential that your attorney is also trained to administer and assess the Standardized Field Sobriety Tests like a police officer.  Our aggressive Dallas DWI lawyer, Murray Bristol, knows the NHTSA DWI Manual.  Therefore, he knows when an officer has failed to administer a SFST properly and can try to either get evidence thrown out of court or show how the tests were not administered properly, so the results of the tests were compromised and therefore invalid.

The following are a brief summary of the three SFSTs:

Horizontal Gaze Nystagmus Test (HGN):
This is where the officer asks a person suspected of driving while intoxicated (DWI) to hold their head still and follow the movement of an object (usually a pen) with their eyes as they move it horizontally and then vertically across the person’s field of vision. What they are looking for is a jerking movement in the eyes (“nystagmus”).  They look for nystagmus when the eye follows the object side to side and the officer looks for 3 clues in both eyes: Lack of Smooth Pursuit; onset of nystagmus prior to 45 degrees; and distinct nystagmus at maximum deviation for a maximum of 6 clues.  If an officer finds 4+ clues, you are considered intoxicated.

The HGN is a scientific test that requires it to be done in a standardized manner.  If the test is not done properly, the results are compromised and should not be admissible in court.

Walk and Turn:
This test, the officer will ask a person first to place his/her right foot in front of the left foot touching heel to toe, to keep your arms down to his/her side while the officer goes through the instructions (Instruction Stance). Then the officer will give the instructions to the person that he/she is to take nine heel-to-toe steps in a straight line (sometimes an imaginary line), turn using a series of small steps, take nine heel-to-toe steps back.

There are 8 clues an officer is looking for (any 2 of the 8 you are intoxicated): can’t balance during instructions; starts to soon; stops while walking; not touch heel to toe; steps off line; uses arms for balance; improper turn and wrong number of steps.  Therefore, a person could fail before they know the test started because they moved a foot out of the stance and started to walk before the instructions were finished (2 clues).

One-Leg Stand:
On this test, an officer will ask the person to lift one foot off the ground at least six inches, for 30 seconds. They are to do this while looking down at their toe, and counting out loud, one-one thousand, two-one thousand, and so on until told to stop. By having the driver perform these two tasks at once (divided attention test) it makes it very difficult for a person who is nervous and never been in this situation before to perform under these hostile conditions.

The problem with the test is that even if the person is able to perform the tasks, they likely will fail because the officer is looking for very subtle clues such as swaying; using arms to balance (even slightly moving the hands or arms), loosing count, or putting the foot down and picking it back up during the tests.  The problem is that the officer does not tell you what he is looking for, so the person does not know how he/she is to pass this test.

Most people without practice cannot perform these tasks as perfectly as expected without having anything to drink, let alone after having a few drinks. The problem can be worse if the person is overweight, has inner ear problems or has problems with their feet or legs.


  • Alphabet Test: C to K;
  • Counting backwards: 38 to 22; and
  • Balance test (Rhomberg) – estimate 30 seconds when eyes closed and head tilted back.


  • Field Sobriety Tests Are Not Scientific
  • The Officer Was Not Properly Trained
  • The Officer Did Not Use Standardized NHTSA Tests
  • The Officer Did Not Properly Instruct You On How To Perform Tests
  • The Officer Did Not Use Objective Standardized Scoring Criteria
  • The Officer Had You Perform The Tests Under Improper Conditions
  • Your Age Or Weight Make You An Improper Candidate For Tests
  • You Have A Physical Disability That Makes You An Improper Candidate For Tests
  • You Have A Psychological Condition That Makes You An Improper Subject For Tests

To speak to knowledgeable, dedicated, and aggressive Dallas DWI lawyer Murray Bristol, please call our office at (214) 880-9988. If you prefer, contact us using the form on this website, and he will contact you promptly for a free consultation.