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Field Sobriety Testing in Houston

Standardized field sobriety tests are roadside tests that officers administer during a DWI investigation in Houston, Texas.  But it's not just Houston officers that use these tests.  They were developed in the 1970s and have been changed very little since that time.  There are three main tests that encompass the standardized field sobriety tests.  These tests are (1) an eye test called the horizontal gaze nystagmus, (2) a walking test called the 9 step walk and turn, and (3) a balancing test called the one leg stand.  

What does standardized mean?

A standardized field sobriety test is one of the three tests mentioned above.  They are "standardized" in that the government conducted various studies in the 1970s to determine if they could associate a certain level of motor performance on tests with blood and breath alcohol levels.  The tests look for "clues" that may indicate intoxication and they allow the officer to observe these clues and form an opinion about the defendant's level of intoxication.  

Horizontal Gaze Nystagmus

The first test that officers typically perform is called the HGN which is short for horizontal gaze nystagmus.  This is an eye test were the officer holds a stimulus (typically a pen or the officer's finger) 12-15 inches away from the person's nose and slightly elevated.  Then the officer asks the person to follow the stimulus with their eyes and their eyes only and to keep their head still.  The officer is checking for an involuntary jerking of the eye.  The theory is that when alcohol starts to influence your body the first muscles that are inhibited are ones with fine motor function.  For example an officer may ask you for your driver's license just to see if you're able to easily produce it from your wallet or if you fumble around and show a loss of finger dexterity.  The muscles which control your eyes are fine motor skill muscles and when they are inhibited by alcohol they can produce HGN. 

The officer is looking for 6 clues (3 in each eye) during the HGN.  First the officer looks to see if your eyes track smoothly from left to right and back.  If they cannot track the stimulus smoothly this is counted as a clue against you.  The second part of the test is when the officer asks you to look all the way to the right or left.  This is called "maximum deviation." If your eyes jerk when they are looking all the way to the edge of your field of vision then this is the second clue for each eye.  Finally the officer approximates a 45 degree angle from your face to your shoulder and if the officer can see nystagmus occur in the eye prior to the stimulus being extended from the center to 45 degrees then you will be marked as having the last clue. 


Almost all DWI arrests are reported to have 6/6 clues on the HGN and officers commonly call it the most reliable test.  It is however the least verifiable and should be performed by an expert or a doctor.  There are many things that can produce nystagmus other than alcohol.  For example optokinetic nystagmus is virtually indistinguishable from HGN and it can be produced simply by the eyes tracking quickly moving objects like a train passing in front of a railroad crossing.  

9 Step Walk and Turn

The second test officers will perform is typically the 9 step walk and turn.  They will ask the detained person to place their left foot on an imaginary (or real) line.  Then place your right foot in front of your left with your arms to your side and remain in that position until the officer completes his instructions.  If you step out of this awkward position the officer will count it against you even if he never explains what he is looking for during the test.  Next you will be asked to take 9 steps down the imaginary line touching heel to toe on each step and when you reach your ninth step to keep your lead foot planted and turn around using a series of small steps and then proceed back down the line taking 9 steps back.  The officer will ask you to keep your arms by your side during the test and ask if you understand the instructions.  The officer will then look for the following clues. 

  • Steps out of the instructional position

  • Starts too soon

  • Stops while walking

  • Fails to touch heel to toe on every step

  • Takes wrong number of steps

  • Makes an improper turn

  • Uses arms for balance

  • Steps off the line

If the officer sees two or more of these clues he is going to mark you down as intoxicated.  That means you can get the test 75% right and still fail.  Notice how many of these clues are never mentioned during the instruction phase.

One Leg Stand

The final test that officers typically administer is the one leg stand test.  It is a balancing test where the officer asks you to lift one foot of your choosing approximately six inches off the ground, point your toe, and count in the following manner 1001, 1002, 1003, and so on until the officer tells you to stop.  You'll be instructed to keep your arms to your side during the test and that you can begin when the officer tells you.  

The officer will be looking for the following clues during the test: 

  • Sways while balancing

  • Puts foot down

  • uses arms for balance

  • hops

After watching thousands of DWI videos the most damaging clue to see in this test is hopping.  Almost every person accused of DWI puts their foot down prior the 30 seconds that the officer is testing.  Even gymnasts use their arms for balance, but if you use them on this test the officer is going to count it against you.  If the officer observes two or more clues on this test he is going to believe that you are intoxicated according to the standardized field sobriety testing manual.  

What should you do if an officer asks you to perform field sobriety tests?


Many clients feel like they have failed when they agreed to perform the tests and ask me if they should have refused.  There is no right or wrong answer to this problem.  If you look fairly sober on video when performing the tests an attorney might rather have you perform them.  If it isn't going to go well it is probably better to refuse.  These choices are extremely difficult because if you refuse to participate in any of the tests the officer is almost certainly going to arrest you.  There is no law that requires you to perform the tests and the less information that the officer has to write a warrant the less likely a judge is going to sign off on one to take your blood.  If you've or a loved one has been arrested for DWI call us today so we can help.  Brian and Luis are both former prosecutors and members of the vehicular crimes team which specialized in driving while intoxicated cases. 

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