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  • Brian Foley

Montgomery County DWI Attorney - Standardized Filed Sobriety Tests

Montgomery County DWI Attorney - Brian Foley Board Certified in Criminal Law.

Montgomery County, Texas has DWI arrests every day. Before each arrest officers will almost always follow the same protocols. First if there has been a traffic accident officers will respond to the scene and determine who was driving. If they smell alcohol on the breath of one of the driver's they are going to do what they call "SFSTs." SFSTs are Standardized Field Sobriety Tests.


There are three standardized field sobriety tests regularly administered by peace officers across the United States. They are:

  1. The horizontal gaze nystagmus test;

  2. The 9 step walk and turn test; and

  3. The one leg stand test.

These tests were developed in the 1970s so that they might be administered to people across the population and allow an officer to fairly evaluate if a suspect is intoxicated. However these test are supposed to be done according to proper guidelines otherwise the validation studies that underly them cannot be applied with the same force. That means that if the officer doesn't deliver the instructions properly or the person isn't a proper candidate to take the tests then the results can be skewed. For example. Someone who is obese should not be asked to do the 9 step walk and turn or the one leg stand. Someone who has just been in a serious car accident and may have brain trauma should not be asked to do the horizontal gaze nystagmus test.


The HNG test or the horizontal gaze nystagmus test is an eye test. An officer will ask you to follow a light, or some other stimulus as he moves it from side to side approximately 12 inches from your face. The officer is checking for involuntary jerking of the eyes. This involuntary jerking is called nystagmus. There are many things that can produce nystagmus. For example if your eyes are following a train that is passing by and jerking left and right to follow it then we would call that optokinetic nystagmus. An officer checks each eye for smooth pursuit, and sustained nystagmus at "maximum deviation." Sustained nystagmus at maximum deviation means does your eye shake when you move it to the side all the way. Finally the officer will check for involuntary jerking in the eye prior to an approximated 45 degree angle. There are six possible clues on the HGN, three in each eye. I have found that almost all defendants arrested for DWI are reported to have had all 6 clues.


The 9 step walk and turn test is a divided attention field sobriety test. The officer will instruct you to place your left foot on an imaginary line and put your right foot in front of your left on that line and stay in that position with your arms to your side. This is called the ready position. The officer will be looking to see if you stay in that position and count it as one of eight possible clues on the test. The official statistics of this test say that if you have 2 or more clues out of 8 then you are intoxicated. That means you can get 75% of the test correct and still fail. The other clues the officer looks for is taking the wrong number of steps, an improper turn, using arms for balance, failing to step touching heel to toe, steps off the line, stops while walking, and starts too soon. In my experience this is one of the most subjective tests used by officers and juries in making decisions in an intoxication offense.


The one leg stand test is also a divided attention test where the officer is looking for clues. On this test the clues are, puts foot down, raises arms for balance, sways while balancing, and hops. Here the officer is looking to get at least 2 out of 4 of these clues to indicate to him that you are intoxicated. The least likely clue to find on this test is hopping. I've reviewed thousands of DWI videos and hopping is one of the clues that stands out the most in those videos.


Well I can tell you what is supposed to happen is an officer looks for clues and then takes the information from the three standardized field sobriety tests and other information he has gathered and evaluates the totality of the circumstances to determine if he believes you have lost the normal use of your mental and physical faculties.

In practice I think more and more that what happens is the officer goes through his training on the field sobriety tests and at the end makes an arrest unless you did them perfectly. Even then he'll make an arrest for DWI if he has suspicion based on something else you said or did.


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