Standardized Field Sobriety Tests

Standard Field Sobriety Tests (SFSTs)

Contrary to popular belief the roadside tests conducted on suspected drunk drivers are completely voluntary. You do not have to do these! Officers often tell suspects that if they refuse “testing” they will lose their license “automatically” for one year. This is the officer’s way of getting you to take roadside sobriety tests and this statement is only half true. It is true that you can lose your license if you refuse a chemical test; however, there are no additional penalties for refusing voluntary field sobriety tests. That is why they are voluntary. Understand that your performance on these tests can and will be used against you.

In Michigan, the officer must establish probable cause before they can arrest you and require you submit to a chemical test. The most common form of establishing probable cause is through the performance and evaluation of voluntary roadside maneuvers, also known as Standard Field Sobriety Tests. These tests were developed and formulated by the National Highway Traffic Safety Administration (NHTSA) and have been adopted throughout the country. These tests are designed to detect impairment due to alcohol consumption.

Attorneys at The Law Offices of Barton Morris are NHTSA certified in Standardized Field Sobriety Testing. This training is very similar to what Michigan law enforcement receives in order to be certified in SFSTs. There are around a dozen or so maneuvers that are used by local law enforcement to determine impairment and/or intoxication; however, there are three standardized tests that are most commonly used in Michigan. The Standardized Field Sobriety Test (SFST) is a battery of three tests administered and evaluated in a standardized manner to obtain validated indicators of impairment and establish probable cause for arrest. These tests were developed as a result of research sponsored by the National Highway Traffic Safety Administration (NHTSA) and conducted by the Southern California Research Institute.

The following three tests compose the SFSTs:

  • Horizontal Gaze Nystagmus (HGN)
  • Walk-and-Turn (WAT)
  • One-Leg Stand (OLS)

These tests are administered systematically and are evaluated according to measured responses of the suspect.

HGN Testing

Horizontal gaze nystagmus is an involuntary jerking of the eye that occurs naturally as the eyes gaze to the side. Under normal circumstances, nystagmus occurs when the eyes are rotated at high peripheral angles. However, when a person is impaired by alcohol, nystagmus is exaggerated and may occur at lesser angles. An alcohol-impaired person will also often have difficulty smoothly tracking a moving object. In the HGN test, the officer observes the eyes of a suspect as the suspect follows a slowly moving object such as a pen or small flashlight, horizontally with his or her eyes. The examiner looks for three indicators of impairment in 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. NHTSA research found that this test allows proper classification of approximately 88 percent of suspects with BAC’s of .08 or greater (Stuster and Burns, 1998). However, there are many forms of nystagmus, and nystagmus is a fairly common medical condition that exists in thousands of people who are not impaired and have not consumed alcohol or drugs. You do not have to be impaired or under the influence to have nystagmus.

Walk and Turn

The Walk-and-Turn test and One-Leg Stand test are “divided attention” and “balancing” tests. 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). However, this test is not as simple as it seems. The officer oftentimes attempts to deceive or trick the subject by giving incomplete or inconsistent instructions. People who are not impaired may have difficulty performing this test if they have certain medical conditions, equilibrium or balancing issues or are overweight.

One Leg Stand

The Walk-and-Turn test and One-Leg Stand test are “divided attention” and “balancing” tests. 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). Once again this test is not as simple as it sounds. A lot of people who are not impaired will struggle to balance on one leg for 30 seconds. Overweight subjects, people with medical conditions and equilibrium issues and weather conditions can and will impact the performance of subjects on this test.

Overall Reliability

NHTSA claims that when all three (3) tests are combined the overall efficiency at identifying BACs above .08 is 91 percent. These numbers are very misleading as they assume the tests were performed correctly by the officers in ideal weather and roadside conditions with subjects who do not have any possible medical conditions that could explain false positives or reasons for poor performance other than intoxication.  NHTSA is relying upon a study that has not even come close to meeting the scientific standards set forth for all other studies to be considered valid.  These studies have not been peer reviewed, the subjects were not random, the study was not a double blind study, etc.