| For persons accused of DUI in California, Field Sobriety Tests are generally used to determine if a person has been driving while intoxicated, and whether or not there is probable cause to arrest the driver for DUI.
Most drivers are not aware that there are only three recognized field sobriety tests. 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. A formal program of training was developed and is available through NHTSA to help police officers become more skillful at detecting DUI suspects, describing the behavior of these suspects, and presenting effective testimony in court. Formal administration and accreditation of the program is provided through IACP. Unfortunately, many officers either did not attend the formal training, or relax the strict standards of the three tests, sometimes adding tests that are not recognized. The three tests of the SFST are:
- Horizontal Gaze Nystagmus (HGN)
- Walk-and-Turn
- One-Leg Stand
These tests are administered systematically and are evaluated according to measured responses of the suspect.
Testing Accuracy:
The NHTSA manuals (plural here, because 6 separate versions have now been released) say that if the FST tests are not performed properly, or if conducted without adhering to the training protocols, such actions “compromise” the validity of these evaluations.
The HGN evaluation, when performed correctly on proper subjects, had a 77% “claimed” reliability rating. The Walk-and-Turn exercise, when conducted properly on a qualified subject on a dry, level surface, was found to be 68% reliable. The One-Leg-Stand exercise, when conducted properly, on a qualified subject on a level, dry surface and under proper instructions and where correctly demonstrated and scored, reportedly yields about 65% reliability. Cumulatively, if all are done correctly, up to 83% correlation to a BAC of 0.10% or more may be expected.
Knowledgeable criminal defense lawyers know that 98% or more of the officers administering these evaluations do them wrong, or conduct them in a manner (or on a test subject) not approved by the SFST manual, or grade the evaluations improperly, as per the manual, or ALL OF THE ABOVE. When done incorrectly, these evaluations have ZERO predicted reliability.
Also, recent research and scientific review of the testing protocols and scoring methodology have brought the NHTSA “Standardized Field Sobriety Tests (“SFSTs”) into serious question. More and more courts are now saying “no” to these questions. In a recent New Mexico case, a high-level court has declared that the person who “developed” the tests (Dr. Marcelline Burns) was not qualified to testify as an expert witness about the scientific principles behind the HGN test. (Lasworth v. State, 42 P.2d 844 (N.M. App. 2001).
The Voluntary Nature of FST Tests:
Recognize that these tests are completely voluntary. These voluntary “tests” (yes, voluntary) are developed NHTSA and implemented by police agencies to assist law enforcement officers in making roadside determinations as to whether a motorist is under the influence of alcohol or drugs. Through the performance of these tests or evaluations, the officer subjectively determines how the motorist reacts to and performs the requested tasks.
Almost EVERY knowledgeable DUI / DWI attorney will say to you, “NO. Don’t attempt ANY ‘field tests’ — EVER.” That is because many studies have concluded that the SFSTs are “designed to fail” even sober drivers.
A motorist's alleged poor performance on field evaluations may provide the “probable cause” (legal justification) an officer needs to arrest a person for impaired driving and may also become part of the proof used to later convict the person at trial. Therefore, it is very important that, in defending you, your defense attorney know as much or more about these tests as the police, if he or she is going to defend you.
DUI defense counsel usually challenges the subjective nature of the evaluations, the accuracy of the principles behind the tests, the accuracy of the administration of the tests, the credibility of the officer who “requested” the tests, and challenge all circumstances connected with the evaluations. An attorney representing you must attack the factual and legal issues that may arise regarding the officer's scoring and evaluation of the field tests.
The reason that most credible scientists across America (and in other countries) are unwilling to categorize field tests — even NHTSA's tests — as being “scientific” is that too many variables are involved in roadside testing to ever eliminate pure chance and non-controlled circumstances from the equation (e.g., environmental conditions such as lighting and roadway slope).
Even NHTSA admits that under optimal conditions (i.e., in an air-conditioned, well lighted room) 35% of sober, drug-free subjects get inaccurate results on the one leg stand test, 32% of sober subjects get flawed results on the walk and turn, and 23% of sober subjects are inaccurately said to be “over the legal limit” on the horizontal gaze nystagmus test. By comparison, polygraph (lie detector) tests are more than 90% accurate when conducted by a qualified operator), and (absent a stipulation by both parties) are still not permitted into evidence by most courts. |
