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Field Sobriety Tests

As part of a DUI investigation, law enforcement officers use both Standardized Field Sobriety Tests (SFST) and, sometimes, non-standardized tests, to assist in determining whether a driver is drunk or impaired in some manner.  SFST's are usually requested by the officer if the officer smells alcohol or observes some objective symptoms that the driver may have been drinking or using drugs.  The tests are supposed to assist officers in determining a person's level of impairment.


There are three SFST's that officers utilize during a DUI investigation: the Horizontal Gaze Nystagmus (HGN), the Walk-and-Turn (WAT), and the One-Leg Stand (OLS).  These are the only three field sobriety tests endorsed by the National Highway Traffic and Safety Administration (NHTSA), thus they are referred to as "Standardized" Field Sobriety Tests.  

Horizontal Gaze Nystagmus 

HGN is an involuntary jerking of the eye that occurs when the eyes move from side to side.  The HGN test requires the driver to look forward at a small object, usually the officer's finger, pen, or a small flashlight.  The officer then asks the driver to hold their head still and follow the object with their eyes as he moves it side to side.  The involuntary jerking will be exaggerated if a person is impaired by alcohol.  Specifically, officers giving the HGN test look for three indicators of impairment in each eye:  1) an inability to follow the moving object smoothly; 2) distinct eye jerking when the eye is at maximum deviation, which is the point at which the eye has moved fully to one side and cannot move any further; and 3) whether the jerking of the eye is within 45 degrees of center.  


The WAT tests the driver's ability to complete tasks with divided attention, meaning there is both a mental and physical component of the test.  The belief of law enforcement officers is that when you are impaired by alcohol or drugs you typically are unable to perform a task that requires divided attention.  During this test, the driver is instructed to take 9 steps, touching heel-to-toe on each, along a straight line.  The officer will look for several indicators of impairment, including: 1) if the driver cannot keep their balance while listening to instructions; 2) begins walking before the instructions are finished; 3) stops while walking to regain balance; 4) does not touch heel-to-toe; 5) uses arms to balance; 6) steps off the line; 7) takes the wrong number of steps, either too many or too few; and 8) makes an improper turn.

One-Leg Stand 

The OLS is also a divided attention test.  The driver is instructed to stand with one leg in the air approximately six inches off the ground.  The person is instructed further to count aloud as follows: one thousand-one, one thousand-two, one thousand-three, etc. until the officer tells them to stop counting and put their foot down.  The officer looks for four specific indicators of impairment, including: 1) swaying while balancing; 2) hopping to keep balance; 3) using their arms to keep balance; and 4) putting the foot down.  


Although considered standardized, these tests have been widely criticized as designed for the driver to fail.  These are not pass/fail tests.  Scoring for the indicators of impairment can vary widely by different agencies and by the training and experience of the officer administering the tests.  Additionally, there are many factors that can affect a driver's performance on the SFST's.  For example, age, injury, or disease can affect the person's ability to successfully complete the OLS or WAT.  Similarly, an uneven surface or poor footwear can make these difficult to complete properly.  During the HGN test, a person suffering from an eye condition or disease that affects their ability to follow the object could display the indicators which could lead an officer to improperly conclude that they are impaired.  A person with difficulty hearing may not understand the instructions that are given and, as a result, not do the tests properly.  


There are a number of other "non-standardized" field sobriety tests that some law enforcement agencies use.  These tests include the Rhomberg balance test (standing with feet together, tipping head backwards, and counting silently to estimate when 30 seconds have elapsed), closing the eyes and touching finger to nose, reciting the alphabet, and counting backwards.  These "other" field sobriety tests have not been standardized by NHTSA, meaning police officers are not required to follow any specific guidelines or told what particular clues to look for when giving them.  The lack of standardization of these tests results in irregularity and unpredictability of the testing process, even more so than the standardized tests (HGN, OLS, WAT).  These "non-standardized" FST's are even more susceptible to attack by a good DUI lawyer.  


The Preliminary Alcohol Screening Test (PAS) is also considered a field sobriety test and is administered during the DUI investigation.  The PAS is a portable handheld breathalyzer machine that measures a person's blood alcohol level.  This test is usually given following the conclusion of the other field sobriety tests if the officer believes the driver has been drinking alcohol and their ability to drive has been impaired.  All field sobriety tests are given during the DUI investigation and before the driver is arrested.  It should be noted that all field sobriety tests are voluntary unless the driver is on probation for a prior DUI or alcohol related conviction.  


If you have been arrested on suspicion of DUI, speak with a good DUI Lawyer right away.  DUI is not an ordinary traffic ticket in which you consider representing yourself.  CONTACT our office today for a free and confidential consultation.   DUI Attorney Robert D. Berglund represents persons throughout Southern California that have been arrested for drunk driving.


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