This blog is the first part of a three part series discussing the standardized field sobriety tests (or “SFST’s”) used to investigate a DC DUI or DWI stop. If a DC police officer pulls someone over and suspects that the driver has been drinking, the officer will usually ask the person to step outside the vehicle and perform the SFST’s. The SFST’s are made up of three tests. Officers who administer the test have usually been certified by the National Highway Traffic Safety Administration (or “NHTSA”) to perform such tests. Their certification typically consists of a 40 hour training course and a test at the end of the course, which requires them to administer the SFST’s exactly consistent with NHTSA standards.
The three tests consist of the Horizontal Gaze Nystagmus Test (or “HGN”), the walk and turn, and the one leg stand. The walk and turn and one leg stand in the context of a DC DUI stop will be discussed in the next two posts. With each test during the DC DUI investigation, the officer looks for specific cues of impairment to determine whether the person passes or fails to test. Ultimately, if the officer perceives enough “cues” of impairment, he or she will make a DUI arrest.
The HGN is the test where the officers ask you to follow a pen or other stimulus with your eyes. Many people mistakenly think the officer is just checking to determine whether you move your head while following the pen. In reality, the officer is looking for specific types of nystagmus in each eye. Nystagmus is an involuntary jerking of the eyes that is extremely subtle.
The first thing the officer looks for is whether the eyes show a lack of smooth pursuit, which is basically where the eyes move from side to side in a choppy manner (like a broken windshield). The second cue is distinct and sustained nystagmus at maximum deviation. The officer here will leave the stimulus at for about four seconds on each side to see if the eyes jerk in a “distinct and sustained” manner. Finally, the officer checks for “onset of nystagmus prior to 45 degrees.” This final cue is where the officer takes shorter passes on each side to a 45 degree angle to see if nystagmus (or the involuntary jerking of the eye) occurs. The officer looks for these three cues in each eye for a total of six cues.
A typical DUI arrest will occur when the officer observes either four out of six or six out of six cues on the HGN (although I have had a case where the officer still made an arrest after only supposedly observing two of six). Many problems can occur in the officer’s observation and interpretation of the HGN test. For example, the lighting on the side of the road late at night (frequently where the test occurs) may not be sufficient to see these very subtle eye movements. In addition, if the officer does not perform the tests exactly according to NHTSA’s standards, the results from the test are compromised. Moreover, you cannot see what your eyes are doing during the test and typically no independent source confirms the officer’s observations. There are also many things other than alcohol intoxication that cause nystagmus, including, among other things, caffeine, nicotine, and certain health issues.