About Standardized Field Sobriety Tests and their Limitations
If a police officer believes a driver is impaired, he or she conducts a driving while impaired (“DWI”) investigation. There are three standardized field sobriety tests that make up a DWI investigation: the horizontal gaze nystagmus test, the walk and turn test and the one-leg stand test. All three tests should be conducted with each DWI investigation. The tests should be conducted exactly as the officer was trained and in the order shown above. Why? Because that is how the tests were developed and that is how an officer is trained to do them. Deviations from this procedure undermine any conclusions that can be drawn from the tests. When the tests are over, a preliminary breath test may be administered, but that should have no bearing on an officer’s decision to make an arrest.
Horizontal Gaze Nystagmus
The horizontal gaze nystagmus (“HGN”) test is the first standardized field sobriety test (“SFST”) administered by the officer when investigating a possible DWI. In this SFST, the officer moves a pen or his finger, referred to as a stimulus, back and forth in front of your face while you stand straight and keep your head still. The officer is not checking to see if your eyes can follow the stimulus. He or she is looking for an involuntary jerking in each eye while your eyes follow the officer’s pen or finger. The three observations the officer is looking for are lack of smooth pursuit, distinct and sustained nystagmus at maximum deviation, and onset prior to 45 degrees. What do these mean? Your eyes jerk from side to side instead of following smoothly, your eyes jerk back and forth when looking all the way to the side, and your eyes start jerking back and forth before they get all the way to the side.
Now, there are many and serious problems with this test. Nystagmus is a clinical term for an involuntary jerking of the eyes. Horizontal gaze nystagmus is just one of more than 40 different types of nystagmus, and HGN is induced by a certain alcohol concentration in the body. It used to be that officers were not considered qualified to administer this test because they did not have the medical experience or training to give such a level of expert testimony on the matter. The North Carolina legislature solved this problem for prosecutors by rewriting the rules of evidence to allow officers to testify about HGN with a minimum level of basic law enforcement training. Read this blog, try the test out on your friends, and maybe you can be an HGN “expert,” too.
In nearly every DWI arrest, we expect to see these observations reported as present in the DWI investigation, but there are challenges to the results. First, there is no way to distinguish one type of nystagmus from another, such as optokinetic nystagmus which is induced when the eyes follow an object rapidly moving out of the field of vision. A passing car may induce optokinetic nystagmus. The flashing lights on the officer’s police cruiser may induce nystagmus. Nystagmus is nystagmus. It all looks the same. I once used a neurologist as an expert witness who told me that 50% of his patients have resting nystagmus. That means 50% of the people he sees exhibit the same nystagmus the HGN test is looking for with no alcohol in their system.
Notwithstanding the reasons an officer should not even be allowed to testify about nystagmus, there are often problems with how this test is administered. There is a very specific way the test must be administered for the observations, or perceived observations, to have any validity. Did the officer do a medical check before starting the test? Did they move the stimulus too fast? Too slow? Did they hold the stimulus at maximum deviation long enough? Too long? Did they pause to confirm onset before 45 degrees? Did they check for multiple observations in a single pass of the stimulus? Improper administration of this test can actually induce nystagmus, but not horizontal gaze nystagmus. HGN is the only one that counts, here. If the HGN test is not done right, it has no validity.
Walk and Turn Test
The second standardized field sobriety test is the walk and turn (“W&T”) test where you walk in a straight line as if on a tightrope, turn, and then walk back on the line. First you are placed in an instructional position with your left foot on a line, real or imaginary, and your right foot in front of the left touching heel-to-toe. After being instructed and given a demonstration, you begin, taking nine steps down heel to toe, on your ninth step taking a series of small steps with your right foot to turn around, and then taking nine steps heel to toe back. Beware: the police officer is looking for more than whether you can walk the line without falling down.
There are eight different observations to this test, and you will not be told what the testing criteria is. The 8 clues are: starts test too soon, cannot keep balance during the instructional phase, misses heal to toe while walking, steps off line while walking, uses arms for balance, stops walking, improper turn, incorrect number of steps.
During the instructional phase of the W&T test, you will not be told the specific criteria you are being graded on. You will not be told that if your heel and toe are more than ½ inch apart it is a clue of impairment. It is effective in hearings or trials to have the officer step off the witness stand and demonstrate the difference between ½ inch and one inch because it is barely noticeable from any distance. This awkward gait would have you worrying between either stepping too far apart or stepping on your own foot and tripping. Does stepping 1 inch apart versus ½ inch apart mean someone is impaired? No, it does not.
Other mistakes on the W&T test can often be attributed to just not understanding the instructions. People don’t normally walk a tight rope and turn around in such an awkward manner. Police officers will testify as if this is a perfectly normal thing and it is inconceivable that someone who is not drunk cannot follow their directions, but that fails to account for the stress of being subjected to a DWI investigation. People are always nervous while performing a DWI investigation. They do not feel comfortable asking the right questions to be sure they understand what is being asked before performing the test. The real question should be whether you were able to perform in a normal manner. Were you able to walk down and back without tripping or stumbling?
Like the HGN test, police officers are trained to administer and interpret the W&T test in a standardized manner. There is no room for their own subjective interpretation. If the officer does not instruct properly or demonstrate properly, how can they grade you on the test? If the W&T test is not done properly, it has no validity.
One-leg Stand Test
The third and last standardized field sobriety test is the one-leg stand (“OLS”) test. Many in the legal community on all sides consider this the hardest of the three SFSTs. With the OLS stand test, even more than the other two SFSTs, physiological factors such as weight, fitness, age, and dexterity can cause a false-positive.
With the OLS test you are instructed to stand with your feet together and arms by your side. When the officer tells you to, you are to raise one foot off the ground and count using the “one one-thousand, two one-thousand, …” counting method. The officer times 30 seconds for the test but does not tell you how long to stand on one foot. While performing the test, the officer will often shout additional instructions at you. “Point your foot straight.” “Don’t bend your knee.” “Raise” or “lower” your foot. These additional commands are often not part of the standardized way of administering and interpreting the test. They are just distractions.
There are only four things the officer is looking for in the OLS test: sways while balancing, uses arms for balance, hopping, and puts foot down. All those other things an officer is telling you to do are not statistically validated signs of impairment. They are distractions from your true performance of the test. The most reprehensible command barked while you are performing the OLS test is to not bend your knee. A slight bend to the leg planted on the ground is natural and allows you to stand for 30 seconds in such an awkward manner. Straightening the leg is not part of the test and will almost always cause certain failure. This is why you are told to not bend your knee. Fun fact, when an officer is asked to get down from the witness stand and demonstrate the OLS test, they bend their knee, too.
Preliminary Breath Test
The preliminary breath test, or PBT, is a road-side analysis of your breath to confirm the presence of alcohol. It is not a reliable test of actual alcohol concentration. In practice, most officers do, in fact, rely on the test for its numerical value and use it as a basis for their decision to arrest. This is wrong.
The purpose of a DWI investigation and the standardized field sobriety tests is for the officer to form an opinion not just whether there is enough evidence to believe you are impaired, but that you are impaired on an impairing substance. Medical impairment is not grounds for a DWI charge. If the officer believes that alcohol is the impairing substance, the PBT is supposed to be a tool to confirm the presence of alcohol in your system. It is not supposed to establish an alcohol concentration. The PBT is supposed to be administered after the SFSTs as a confirmation test. (If a substance other than alcohol is suspected as an impairing substance, a drug recognition expert should be called to determine what the impaired substance is.)
In practice, most officers give the PBT test before beginning any of the SFSTs. Once they do, their mind is made up. Confirmatory bias leads the officer to believe that anything they see in the SFSTs then must be evidence of impairment, which is wrong.
The PBT result is inadmissible in court. The only thing the officer can testify to is whether it was positive or negative for alcohol. Simply having alcohol in your system is not against the law unless you are under 21. It is only against the law to drive after you have consumed a sufficient quantity of alcohol to be noticeably impaired or above a .08 alcohol concentration, and a PBT cannot establish either of these factors. While this test is supposed to provide confirmation of the presence of alcohol after a decision to arrest has already been made, it is all too often used as the foundation for the officer’s decision to make a DWI arrest.
Are there other field sobriety tests?
The HGN test, W&T test, and OLS test are the only standardized field sobriety tests. Studies were commissioned that purported to give these tests statistical validity for the detection of impaired drivers. Now, these studies are not without issue. After all, they were funded by law enforcement. But what this means is that these are the only tests that have any perceived validity for DWI investigations. There is no validated alphabet (or “ABC) test, and there is no validated counting backwards test. Any “test” beyond the SFSTs has no basis for reliability.
Attacking the DWI Investigation
At Landon White Law Firm, we have a deep understanding of the proper procedures for administering and interpreting the SFSTs. Mistakes are made in most DWI investigations. We find these mistakes, and we challenge them in court. Successfully spotting these issues and challenging them in court can lead to a dismissal of the DWI charges or a verdict of not guilty.
Written by Landon White.
