Validity of DUI Field Sobriety Tests

You're pulled over for a missing tag light on your way home from dinner where you've had a glass or two of wine and the officer wants you to do some tests to make sure you are safe to drive.  You perform the test, you think you've done fine, but the officer places you under arrest for DUI.  So, what are these tests and how valid are they? 

    The National Highway Traffic Safety Administration, or "NHTSA," developed three standardized field sobriety tests back in the 1970s that when administrated following the same procedures and protocols are supposed to be a valid indicator of when an individual's blood alcohol concentration is over a 0.08.  Those three tests are the Horizontal Gaze Nystagmus Test (or "HGN"), the Walk and Turn Test, and the One Leg Stand Test.  In NHTSA's original validation studies of these tests it was determined that the HGN test was accurate 77% of the time, the Walk and Turn Test was accurate 68% of the time, and the One Leg Stand Test was accurate 65% of the time. 

    The last two tests, the Walk and Turn and One Leg Stand tests, are referred to as divided attention test.  This means the person is having to divide their attention between a physical task, like walking a straight line or standing on one foot, while completing a mental task, like counting, or following directions.  These tests have been shown to be invalid for individuals who are overweight or who are over the age of 60. Additionally, it is common sense that different people have varying degrees of coordination and balance.  Some people who are over the legal limit may do very well on these test due to their natural abilities while someone who has a poor sense of balance or lack of coordination may fail the tests even while under the limit.  Other problems with these tests are the way they are evaluated.  For instance, on the Walk and Turn test, some officers believe if a person does not center their foot on the line, the line being the width of the subject's foot, for each step then that is an observed clue of impairment.  NHTSA's protocols actually require the entire foot to be completely off the line in order to mark that clue as observed.  This means a person's foot can actually be 3/4 off the line and that should not be marked against them as a clue, but in many instances it is.  Only one more observed clue on that test and you failed it.   

    There are also problems with the environment in which these tests are administered.  Is every piece of roadway shoulder, parking lot, or street level?  Smooth?  NHTSA says that the area should be level and smooth.  What about the footwear is worn by the person taking the test?  NHTSA says the officer should give the person the choice of removing their footwear.  So, what is easier: doing the test in heels/flip-flops, or walking barefoot on asphalt that has roadway debris on it?  This is just scratching the surface on some of the problems with these two tests. 

    The HGN test commonly referred to as the "eye test," is the only test the officer performs that is claimed to be scientific.  It is supposed to determine if the person's blood alcohol concentration is 0.08 or greater.  This test requires the officer to pass a stimulus (such as a pen, or the officer's finger) back and forth horizontally in front of the person and observe whether or not nystagmus is present.  Nystagmus is defined as an involuntary jerking of the eyes and can be caused by many other things besides consumption of alcohol.  It is present in all individuals at all time, whether they have been drinking or not but it is not normally viewable with the bare eye.  Horizontal gaze nystagmus becomes more pronounced when alcohol is present in the system and it can be observed.  The officer is looking for nystagmus to occur at certain places he moves the stimulus to and if it is present he marks that as an observed clue in the HGN test.   

    The problems with the HGN test are many.  First, the protocols for administering the test must be strictly followed or, according to NHTSA, the results of the test are compromised.  The stimulus is required to be held 12" - 15" away from the test subject's face, and slightly above eye level.  If the stimulus is too high and the person tilts their head back, then nystagmus can occur as a result of "positional alcohol nystagmus" even though the person is under the 0.08 limit.  Additionally, each pass is supposed to take a certain amount of seconds to complete; move the stimulus too quickly or hold the stimulus too long in one location compromises the validity of the test.   

    You need a lawyer who understands how these field sobriety tests are administered.  I have gone through the same NHTSA certification to administer these field sobriety tests that law enforcement officers go through and am certified in the administration of these tests.  Additionally, as a former prosecutor, I used to ride along with many police officers and observe how they give these test in the real world under less than desirable conditions. 

    If you have been arrested for DUI call The Glasgow Law Firm today!