Roadside Sobriety Tests

What you should know about the Standard Field Sobriety Tests

If you are stopped by a police officer and detained for suspicion of DUI, DWAI or DUID, you will most assuredly be asked by that officer to perform the standard field sobriety tests (SFSTs) or roadside maneuvers.  In the state of Colorado, the standard field sobriety tests are a search, which is protected by the 4th Amendment.  The arresting officer needs probable cause to believe that you have been drinking and driving to ask you to perform the SFSTs and then he needs your voluntary consent to administer the SFSTs to you.  Many people find it difficult to tell a police officer “NO” when he or she is asked to perform the standard field sobriety tests; however, it is always in a person’s best interest to refuse to perform the SFSTs when asked to do so.  The SFSTs are strictly voluntary and there is NO PENALTY if a person refuses to perform the tests.

There are three standardized field sobriety tests that are recognized by NHTSA (National Highway Traffic Safety Administration).  The tests are the Horizontal Gaze Nystagmus test, the Walk and Turn test and the One Leg Stand test.  These standard field sobriety tests are supposed to give the officer clues as to whether a person is or is not under the influence of alcohol.  The tests are supposed to require a person to complete different divided attention tasks at the same time and each test has a certain number of clues or indicators that the officer is taught to look for.  Developed in the 1970s, these tests are scientifically validated, and are admissible as evidence in court against any person accused of DUI, if that person decides to take the tests.

The Horizontal Gaze Nystagmus Test (HGN).

Horizontal gaze nystagmus is an involuntary jerking of the eyeball which occurs naturally as the eyes gaze to the side.  Under normal circumstances, nystagmus occurs when the eyes are rotated at high peripheral angles.  However, when a person is impaired by alcohol, nystagmus is exaggerated and may occur at lesser angles.  An impaired person will also often have difficulty smoothly tracking a moving object with his or her eyes.  In the HGN test, the officer observes the eyes of a suspect as the suspect follows a slowly moving object such as a pen or small flashlight, horizontally with his or her eyes.  The officer looks for three indicators of impairment in each eye: 1) if the eye cannot follow a moving object smoothly; 2) if the jerking is distinct when the eye is at maximum deviation; and 3) if the angle of onset of the jerking is within 45 degrees of center.  Studies have shown that a person is likely to have a blood alcohol content (BAC) of 0.08 or greater if, between the two eyes, the officer detects four or more clues. NHTSA research indicates that this test allows proper classification of approximately 77 percent of subjects. However, there are numerous other conditions and substances besides alcohol that may cause exaggerated HGN in a person, such as chronic head trauma, problems with the inner ear labyrinth, chronic eye strain, influenza, vertigo, seizures and the consumption of seizure medications motion sickness, the consumption of excessive amounts of caffeine,  phencyclidine, a variety of inhalants, barbiturates, depressants and others.

The Walk and Turn Test.

In the walk and turn test, the subject is directed to take nine steps, heel-to-toe, along a straight line. After taking the steps, the suspect must turn on one foot and return in the same manner in the opposite direction. The arresting officer looks for seven indicators of impairment: if the suspect cannot keep balance while listening to the instructions, begins before the instructions are finished, stops while walking to regain balance, does not touch heel-to-toe, uses arms to balance, loses balance while turning, or takes an incorrect number of steps, a clue for intoxication is added.  NHTSA research indicates that 68 percent of individuals who exhibit two or more indicators in the performance of the test will have a BAC of 0.08 or greater.

The One Leg Stand Test

In the one-leg stand test, the subject is instructed to stand with one foot approximately six inches off the ground and count aloud by ones beginning with one thousand (one thousand-one, one thousand-two, etc.) until told to put the foot down.  The officer times the subject for about 30 seconds.  The officer looks for four indicators of impairment including:  swaying while balancing, raising the arms above six inches from the side for balance, hopping to maintain balance, and putting the foot down.  NHTSA research indicates that 65 percent of individuals who exhibit two or more such indicators in the performance of the test will have a BAC of 0.08 of greater.



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