Criminal defense in Austin Texas.

Field Sobriety Tests – HGN

Posted By on January 21, 2009

If you get pulled over by the police, the last words you want to hear are, “Please step out of the car.”  (With or without the “please”.)

In Austin, the police use a standardized form, which later becomes the basis for the PC affidavit, (or “Affidavit for Warrant of Arrest and Detention”) when they’re investigating somebody for DWI.

The form contains a series of boxes the officer can check off, for things like “smell of alcohol,” and “slurred speech,” but more importantly, it sets out the results of the most-used field sobriety tests, which are:

  • HGN (Horizontal Gaze Nystagmus)
  • Walk and Turn
  • One Leg Stand
  • Romberg Balance

Horizontal Gaze Nystagmus is the one where they wave a pencil, or some other object, in front of your eyes.  The purpose is to see whether you can track the object smoothly.  If not, that’s taken as a sign, or “clue” that you’re DWI.

Strobe lights can make a moving object appear to have stopped

HGN is rarely videotaped (though there’s no reason it can’t be done).  So you’ve got to rely on the arresting officer to tell you whether somebody’s eyes were twitchy or not.  It can be caused by a wide range of factors, including head trauma and influenza (flu) and eye strain.  It’s not supposed to be done in front of passing cars, or strobing lights (like the kind on police cars).  But it’s done that way all the time.  And even its proponents will tell you it can detect whether you’ve been drinking, but it can’t say how much.  How much, it turns out, is actually the part that matters.


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