The standard field sobriety test is a series of three exercises: (1) Horizontal Gaze Nystagmus; (2) Walk and Turn; and (3) One-Leg Stand. These exercises are theoretically designed to catch impaired drivers by testing a person’s cognitive and physical abilities—how a person is able to process data and physically perform. Field sobriety exercises are legal; however, a person is not required by law to perform them and there are no ramifications if you elect not to participate.
The Horizontal Gaze Nystagmus (HGN) exercise, commonly referred to as the “follow the pen test,” is supposed to uncover if you have an involuntary jerking of the eye, which in theory is supposed to illustrate that a person is under the influence of alcohol or other drugs. However, certain other substances—nicotine, aspirin, caffeine—can cause the same effect. Further, being tired can also cause nystagmus. During the HGN test, the law enforcement officer instructs the person to put their hands by their sides, keeping their feet together, and to keep their head still while the officer moves the stimulus 12 inches from the person’s nose, slightly above the person’s eyes. The officer moves the stimulus during 14 or more passes in front the person’s eyes and looks to find this involuntary jerking of the eyes. Once the aforementioned is completed, impairment is determined based off of clues of nystagmus at maximum deviation, the onset of nystagmus prior to 45 degrees, or a lack of smooth pursuit.
Under the law, Horizontal Gaze Nystagmus testing is considered scientific evidence—unlike the Walk-and Turn and One-Leg Stand tests—for which there is danger of unfair prejudice and confusion to jury if admitted as lay observations of intoxication in DUI prosecution. Therefore, only an officer that is recognized as a drug recognition expert can testify at trial as to the scientific results of this test. This is important to note because it will determine if more evidence comes in at trial to prove guilt.
Another exercise a suspected impaired driver will be asked to perform is a divided attention test called the Walk-And-Turn. This exercise begins before the person even physically performs the actual walk. The officer is looking for clues of impairment at the instructional phase to see if the person is swaying, unbalanced, or even if the person starts the exercise before the instructions are finished. During the Walk and Turn test, the person is asked to take nine steps—heel-to-toe—along a straight line. After taking nine steps forward, the person must turn on one foot and proceed in the same manner in the other direction. Additionally, the person may be asked to count the steps out loud.
During the entirety of this test the officer is looking for eight clues of impairment. Specifically: (1) if the person is unbalanced during the instructional phase; (2) starting the exercise before the instructions are finished; (3) taking an incorrect number of steps; (4) using arms for balance; (5) failing to touch heel-to-toe; (6) stepping off the straight line; (7) improperly turning; and (8) stopping while walking to keep balance. Two or more of the abovementioned indicators reflect a blood alcohol content of 0.08 or greater, according to research, and are noted by the officer.
The last test that suspected impaired drivers are typically asked to perform is the One-Leg Stand exercise. This is another divided attention test. It requires the person performing the exercise to stand on one foot—approximately six inches off the ground—and to count out loud by thousands for 30 seconds. The person is also timed by the officer for 30 seconds. The officer is looking for the following indicators: (1) using arms from balance; (2) if the person puts their foot down; (3) hopping to maintain balance; and (4) swaying while balancing. The officer will note two or more clues of impairment, which research reflects a blood alcohol content of 0.08 or greater.
The officer will use the results of the field sobriety exercises to determine probable cause for a DUI arrest. An officer can’t arbitrarily ask a driver to perform FSEs without reasonable suspicion of Driving Under the Influence (DUI). Therefore, if an officer does and you perform FSEs, an experience attorney will know to file the appropriate motion—motion to suppress evidence—to aggressively defend your case.