NHTSA Field Sobriety Tests
Police officers typically administer a three test battery of field tests to DUI suspects. These three tests are the one leg stand, the walk and turn, and the horizontal gaze nystagmus test. The three tests are often referred to as NHTSA tests, as the National Highway Traffic Safety Administration, through the Southern California Research Foundation, standardized and developed the three tests battery. Since that time NHTSA has financed and conducted additional validation "studies" on the tests.
Officers love to testify that the tests are validated and standardized. This testimony gives the tests an aurora of scientific validity. The truth is these tests have rarely been subject to real scientific peer review, and when they have, they have been shown to be significantly less reliable than the government promotes them to be. The government (NHTSA) promotes their use based upon studies they sponsored and which were not subject to peer review. Additionally, for the most the part, the raw data relied upon in these "studies" is not available for independent review or analysis. These "validation studies" smack of bias as they are designed and conducted by the very same parties interested in using the tests for DUI enforcement.
The underlying concept of the field tests is they purport to test divided attention, which is necessary in driving. For instance, when you drive, you must divide your attention between several tasks, such as steering, navigating, braking, and signaling.
At trial, Officers routinely are permitted by judges to testify as experts on alcohol intoxication. The officers testify alcohol impairs a person's ability to divide attention or multi-task. They then detail a DUI suspect's poor performance on these "tests." The officers, under the careful questioning of prosecutors, provide little or no information regarding the limitations of the tests. Jurors are often left with the impression the only real cause of poor performance on these tests is alcohol intoxication.
Of course, this is not true. What the officers will never volunteer, and don't want the jury to know is that many people perform poorly on these tests when they are not under the influence of alcohol or any other mind altering substance. The fact is, not everybody has either the physical ability or the divided attention skills to perform the tests.
The tests assume the test subject has the physical ability to adequately perform the tests when sober. This assumption is not always true. Some people are more coordinated than others. Some people can do them, and some can not. Because the tests do not take into consideration a person's actual ability to perform the tests sober, there is no accurate way to judge whether a person is actually impaired in some way. One independent peer reviewed scientific article published on sobriety resulted in police officer finding close to 50% of the test subjects impaired to drive when all subjects were actually stone cold sober.
Are Field Sobriety Tests Voluntary?
Field sobriety tests can be considered mandatory, but at the same time, you can't be forced to do them. If you refuse to do them the police will be deprived of evidence which they are seeking to use against you. Do not assume that because you are sober you will pass them. Remember, the person grading them is biased. The officer conducting the tests most likely has already assumed you are impaired and is building a case against you. While officers often portray themselves as just "seeing if you are OK to drive" they are not neutral.