Don’t Be Fooled, Field Sobriety Tests Do Not Measure Sobriety
The charge of Driving Under the Influence (DUI) requires proof that the driver was impaired or affected by alcohol consumption. This means that the quality and the quantity of the evidence must demonstrate that the driver’s mental or physical functions were impaired to safely operate and control a car. Therefore, it is irrelevant to the charge of DUI to produce evidence that does not measure or demonstrate driving impairment. According to the National Highway Traffic Safety Administration (hereafter NHTSA), standardized field sobriety tests (FSTs) do not measure driving impairment. The common roadside tests include the walk and turn test, the one leg stand test, and the horizontal gaze nystagmus test. Sometimes police officers will add the ABC test, the Rhomberg Balance test, the finger to nose test, and the counting backwards test.
In fact, these agility tests are not “sobriety” tests in spite of their label. This is a government-sponsored “name” for a battery of agility tests to mold the public’s perception in believing that the tests do something that they do not. These tests were designed and are solely used to help an officer estimate a driver’s alcohol concentration and establish probable cause to arrest based on their prediction of an alcohol concentration. See DOT HS 808 839, Final Report, Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent. In other words, the roadside agility tests were developed for the sole purpose of assisting a police officer to make an arrest decision because arrest decisions must be reasonable and must be based on articulable facts.
While many courts and prosecutors consider the roadside tests to be conclusive on the issue of intoxication, nothing could be further from the truth. A good friend of mine cannot and would not “pass” any of the roadside tests because he can barely walk due to all sorts of medical issues, including his weight, but he is a fine driver. As noted in the NHTSA report:
Many individuals, including some judges, believe that the purpose of a field sobriety test is to measure driving impairment. For this reason, they tend to expect tests to possess “face validity,” that is, tests that appear to be related to actual driving tasks….Driving a motor vehicle is a very complex activity that involves a wide variety of tasks and operator capabilities. It is unlikely that complex human performance, such as that required to safely drive an automobile, can be measured at roadside. The constraints imposed by roadside testing conditions were recognized by the developers of NHTSA’s SFST battery. As a consequence, they pursued the development of tests that would provide statistically valid and reliable indicators of a driver’s BAC, rather than indicators of driving impairment.
Therefore, roadside tests do not measure driving impairment. These are not sobriety tests, no matter what the government would like us to believe. Roadside tests are not relevant to the question of whether a driver was impaired or affected to safely operate his vehicle due to alcohol or drug consumption. They are only relevant to answer the legal question about whether or not an arrest was lawful, a standard far below the proof required to convict a person of a crime. Moreover, its use is highly prejudicial because the government would attempt to incorrectly proffer the results of the roadside tests to establish driving impairment due to alcohol or drug consumption.
 State v. Hurd, 5 Wn.2d 308 (1940); State Hansen, 15 Wn. App. 95 (1976); State v. Melcher, 33 Wn. App. 357 (1982).
 ER 403; Compare,State v. Koch, 126 Wn. App. 589, 597, 103 P.3d 1280, 1284 (2005) (HGN cannot be used to show intoxication, only consumption) ; State v. Baity, 140 Wn.2d 1, 13, 991 P.2d 1151, 1159 (2000) (DRE protocol cannot be used to show level impairment and discussed in a scientific aura.)
Image credit to Apasciuto.