Field sobriety tests or FSTs are a series of tests designed to gauge whether or not someone is impaired and safe to drive. The initial field sobriety tests or the SFST, which stands for standardized field sobriety tests, were developed by the National Traffic Highway Safety Administration in the 1970s as part of a campaign to push back against an increased number of drunken driving fatalities and serious injuries in the United States.
The field sobriety tests vary from jurisdiction to jurisdiction and from officer to officer. Typically, they include some physical and some mental tests devised to split the attention of the driver. This means to have them perform a task that may not be intuitive to gauge whether or not they are able to comprehend the instructions and administer the test properly.
The most common field sobriety tests are:
Based on the preference of some jurisdictions and officers, there may also be requests to say a portion of the alphabet, count, or perform other physical tasks, such as touching fingertips or the tip of the nose or doing a finger dexterity test, which is touching the fingertips while counting.
The nine-step walk-and-turn, otherwise known as the walk-and-turn test or the walk the line test, is another common field sobriety test or FST.
Like other tests, this is not a pass-fail test but an indication of impairment test. That means that the officer is not looking to see whether or not someone passes a test, but whether or not the person indicates certain pre-checked clues of impairment while performing the test.
Some of the clues of impairment include:
Officer instructions and test conditions are important to the determination of whether or not it was a proper nine-step walk-and-turn. Anyone who has watched an infomercial or an educational video about drinking and driving has probably seen some version of the nine-step walk-and-turn.
HGN stands for horizontal gaze nystagmus. Nystagmus is a term that refers to the involuntary twitching of someone’s eyes. This is something that officers are trained to look for in DUI stops.
Sometimes people see a horizontal gaze nystagmus test in driver’s education or on infomercials and public safety messages about drunken driving. For the test, the officer holds out a pen or other stimulus and asks the driver to follow the stimulus with their eyes and their eyes only. During this test, the officer is looking for a number of things. Notably, the officer is looking for equal pupil size, smooth and equal tracking, whether or not there is nystagmus at maximum deviations, degrees, and whether or not there is involuntary jerking of the muscles at the side of the eyes. It is a highly-specialized task that requires training.
In many jurisdictions, the horizontal gaze nystagmus test is not admissible for the results of the test, but it may be admissible for whether or not the person follows instructions properly. This is because to properly read the test, it is arguable that one needs a trained optometrist or ophthalmologist who understands eyes and eye health to determine whether or not they are truly looking at nystagmus or some other issue. However, this is a common test and offered in a vast majority of DUI cases.
The third common, standardized field sobriety test or SFST is the one-leg stand test. The one-leg stand test is a device to test both a person’s coordination and balance while splitting two distinct tasks. The distinct tasks illustrated in this test are being able to stand on one foot and counting.
To stand on one foot is the physical part of the test. Typically, it requires the participant to select the foot they are going to use, raise that foot approximately six inches off the ground, and count in a controlled manner. They are told where to look and when to start.
One of the big things that officers look for in these tests along with physical performance is whether or not the person correctly followed instructions. With the one leg stand test, they are looking for whether or not the person started too early, if they raised their foot with the correct amount, and did other things that may indicate impairment versus safe to drive.
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