One of the ways in which the police determine whether a driver is “under the influence” is by making the driver perform field sobriety tests (FSTs). Field sobriety tests were created by the National Highway Traffic Safety Administration (NHTSA) from research started in the 1970s. The purpose of the field sobriety tests is to measure your physical and mental impairment by testing your physical ability to perform certain tasks and your mental ability to follow directions. It is believed that when a person consumes alcohol or drugs, mental impairment will occur before physical impairment. That means, if a person starts to show signs of being physically impaired, then they are already mentally impaired. This is important because for Vehicle Code section 23152(a) – one of the two laws against drunk driving – “under the influence” of alcohol and/or drugs is defined as “physical or mental impairment” that prevents you from driving a vehicle with the same caution that a sober person would use in similar circumstances. So, if the DA can show that you either physically or mentally failed your field sobriety tests, you’re “under the influence”.
NHTSA has developed procedures for administering various field sobriety tests and clues for the officers to look for when the tests are being performed. Although there are several different field sobriety tests and certain police agencies have their favorites, NHTSA has established three standardized field sobriety tests (SFSTs) that all police officers are supposed to give in every (alcohol) DUI case. These three standardized field sobriety tests are Horizontal Gaze Nystagmus (HGN), Walk and Turn, and One Leg Stand.
A driver who is under the influence of alcohol will display nystgamus in his eyes. Nystagmus is the involuntary jerking of the pupils when following a moving object. To conduct this test, the officer will put a fixed object, such as a pen, about six inches in front of the driver’s eyes and then slowly move the object to the left and right. A normal person’s pupils will be able to smoothly track the pen. A person who is “under the influence” will not be able to smoothly track the pen. There will be some lag time between the movement of the object and the movement of their pupils.
In a properly administered HGN test, there are three clues of impairment for each eye — if the eye cannot follow a moving object smoothly, if jerking is distinct when the eye is at maximum deviation, and if the angle of onset of jerking is within 45 degrees of center. Three clues for each eye means six clues total. If four or more clues are present, then NHTSA research indicates that 88% of subjects have a BAC of .08% or higher (Stuster and Burns, 1998). HGN may also indicate consumption of seizure medications, phencyclidine, a variety of inhalants, barbiturates, and other depressants.
The prosecution considers HGN to be the most powerful field sobriety test because it measures an involuntary reaction. In other words, people cannot practice to improve HGN.
The Walk and Turn (WAT) and the One Leg Stand (OLS) are considered a “divided attention” tests. They measure a person’s physical ability to perform tasks and their mental ability to follow instructions at the same time. Since the act of driving is considered a “divided attention” skill, tests that reflect a person’s “divided attention” are considered to be accurate measures of their ability to operate a motor vehicle safely.
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 examiner looks for eight 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, steps off the line, uses arms to balance, makes an improper turn, or takes an incorrect number of steps. NHTSA research indicates that 79 percent of individuals who exhibit two or more indicators in the performance of the test will have a BAC of 0.08 or greater (Stuster and Burns, 1998).
In the One-Leg Stand test, the suspect is instructed to stand with one foot approximately six inches off the ground and count aloud by thousands (One thousand-one, one thousand-two, etc.) until told to put the foot down. The officer times the subject for 30 seconds. The officer looks for four indicators of impairment, including swaying while balancing, using arms to balance, hopping to maintain balance, and putting the foot down. NHTSA research indicates that 83 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 (Stuster and Burns, 1998).
In addition to the standardized FSTs, there are several non-standardized field sobriety tests that certain police agencies prefer. These non-standardized field sobriety tests include:
Overall, there are several big problems with field sobriety tests.
(a) Science is not accurate – field sobriety tests are based on probabilities. But probabilities aren’t foolproof. A test that indicates someone is 65% likely to be over the limit means that 1/3 of the time, an innocent driver is being falsely accused.
(b) Innocent explanation for failure – although alcohol and/or drug impairment can cause a person to fail these field sobriety tests, there are innocent explanations for failure as well. For example, some people have natural nystagmus present in their eyes. Other people have a poor sense of balance or a bad knee (or some other physical problem) and couldn’t perform balance tests even if they were sober.
(c) Tests are not properly administered – the accuracy of the field sobriety exercises depends on the officers’ ability to give instructions properly. Many officers were never trained in NHTSA protocol or were trained so long ago, that they don’t remember how to properly give the test. Poor instructions will account for poor performance.
(d) Wrong clues are observed – the accuracy of field sobriety tests are dependent on clues that have been established by NHTSA. However, some officers do not measure these clues accurately. For example, one of the clues for HGN is that nystagmus is present within 45 degrees of center. But how does an officer measure this? They aren’t using protractors in the field. Officers just guess where 45 degrees is. Another problem is that some officers don’t actually know what clues they are to look for. For example in the Walk and Turn test, officers think that if there is a gap between the heel and the toe, then the defendant has failed the test. However,
(e) Conditions are not suitable – even if everything above were done accurately, field sobriety tests are only useful if they are done in the same conditions as the laboratory. That means proper lighting, even surfaces, good weather, no other distractions and most importantly no fear. The subjects that NHTSA tested weren’t scared out of their minds at the possibility of being arrested. Fear will always affect performance on these field sobriety tests and that is something the prosecution never takes into account.
If you’re facing DUI charges, you need a criminal defense attorney that is intimately familiar with the science behind FSTs. Most attorneys are aware that NHTSA tested the reliability of FSTs back in 1981 and found certain percentages of accuracy for each of the FSTs. However, many attorneys are not aware that NHTSA again tested the reliability of FSTs in 1998 and the more recent research indicates different percentages of accuracy.
Some attorney websites still show the older percentages. These attorneys either don’t know the latest research or are trying to mislead you into thinking that you have a better case than you actually do. Either way, you’ll be getting the wrong results because you chose the wrong attorney.
You want an attorney that is current on the research and law regarding DUIs. With offices in Newport Beach, Riverside and Beverly Hills, Fred Thiagarajah has DUI defense experience in Orange, Riverside and Los Angeles Counties.
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