Attacking Pennsylvania Field Sobriety Tests Designed to Fail

Filed under: DUI Tags: , by Steven F. Fairlie @ January 16, 2012

In a majority of the DUI arrests in Pennsylvania, the driver is asked by an officer to perform a series of physical tests called field sobriety tests (“FSTs”). Theoretically, FSTs are supposed to be a reliable and consistent method to determine if an individual is under the influence as evidence to build probable cause to support a DUI arrest. However, in practice, FSTs are anything but reliable and consistent. Recent studies are bringing these tests, based on 1950-1960’s psychological theory, into question.

The tests themselves can include whatever the examining police officer requests, such as reciting the alphabet, finger-to-nose test, or answering informational quizzes. However, of all the tests employed, only three FSTs have been studied and approved by the National Highway Traffic Safety Administration (“NHTSA”) as having any scientific validity in determining whether a driver is impaired: the (1) One-Leg-Stand; (2) Walk-and-Turn; and (3) Horizontal Gaze Nystagmus test (“HGN”). For a detailed account on these tests, see our informational page, “Field Sobriety Testing and Chemical Testing”.

Even in regards to the three approved tests, reliability has been sharply debated. For example, the NHTSA cautions that in order for any of these three FSTs to have any scientific validity in identifying intoxicated drivers that they must be uniformly administered and objectively evaluated. With nearly a million law enforcement personnel across the United States, uniformly administering and objectively evaluating any subjective test is a challenge in itself.

More importantly, NHTSA acknowledged that even when the three approved FSTs are uniformly administered and objectively evaluated there is a margin of error in falsely identifying sober drivers as impaired drivers. For example, both the One-Leg-Stand and the Walk-and-Turn tests result in a false indication of impairment under the objective scoring system approximately 35% of the time. Even the more scientifically based HGN test produces a false indication of impairment 23% of the time. Therefore, even when the officer does everything by the book, he has a greater than 3/10 chance of arresting a sober driver.

Sobriety test skeptics like former Clemson psychology professor, Dr. Spurgeon Cole, suggest that the margin of error is even more significant. Dr. Cole, an expert in the study of measurements, has been studying FSTs since the ‘80s and has consistently argued that they are neither reliable nor valid. In fact, his research indicates that the tests only give officers a 26% better chance of detecting an actually intoxicated individual than if they randomly guessed. His rationale is based on the theory that FSTs have no norms or average score. Therefore, because we have no idea what the average person could do and nothing to compare results against, FSTs are designed to fail.

To demonstrate his hypothesis, Dr. Cole conducted a study in which 21 sober individuals were asked to perform several FSTs and several “normal-abilities” tests that are well known to individuals (like stating one’s address or walking in a normal manner). These tests were taped and officers were asked to view the tapes, divided between FSTs and “normal abilities” and determine if these individuals were intoxicated. The result, 46% of the officers’ decisions were that an individual was intoxicated from viewing the FSTs. On the other hand, only 15% of the decisions from the “normal-abilities” tests yielded a judgment that the individual was intoxicated. Furthermore, of the 21 individuals performing the test, only three were rated as “unimpaired” by all officers on both the FSTs and “normal-abilities” test.

This data is indicative that judgments of impairment are influenced by the type of test performed. An individual was more likely to be judged as impaired on the basis of FST performance than on performance of the “normal-abilities” tests. Even without alcohol, the number of errors made by individuals who performed the FSTs was sufficient for officers to judge that the individuals had too much to drink. Lastly, Dr. Cole argues that these findings are consistent with other studies reporting sizable percentages of individuals judged to be impaired when they were not (Burns & Moskowitz, 1977; Tharp, et al. 1981).

While the training of officers, standardization of test instructions, administration and scoring may improve the accuracy of FSTs generally, the major obstacle appears to be the test itself. All three of the approved FSTs require unfamiliar and unpracticed motor skills that may put an individual at a disadvantage when performing them. In turn, the officers performing the subjective evaluation are very familiar with the tests and are quick to recognize signs of “impairment.”

Studies like that of Dr. Cole certainly bring the validity of FSTs into question. Nevertheless, they are still used by law enforcement daily. If these subjective tests are in fact unreliable, why do officers administer them? To get you to incriminate yourself. If the officer decides you performed poorly, he can then ask you to take a portable breath test (PBT). If you agree and blow a BAC of .08 or more, you have provided reasonable suspicion to be taken into custody. Once arrested, you are required by law to give an official blood, breath or urine sample, under penalty of a one-year license suspension if you refuse. Therefore, what should you do if you are suspected of DUI?

First, submission to FSTs is voluntary and not required by law. The officer may request them, but failure to perform them correctly, judged subjectively by the officer, may be used as additional evidence to build probable cause to support a DUI arrest. A police officer may interpret a refusal to perform FSTs as suspicious and therefore probative of intoxication, but a person who is intoxicated should not submit to FSTs in hopes of passing them.

However, even if you submitted to FSTs, there are a number of ways that they can be attacked. The NHTSA outlines procedures in administering the approved FSTs. If there is a deviation from NHTSA protocol in administering or scoring the test, the validity and reliability can be attacked. The subjective nature makes interpretation of FSTs highly variable. Furthermore, there are many factors unrelated to intoxication that could negatively affect an individual’s performance. Many people are clumsy, may be very tired, or may have had a past medical condition, which would affect their ability to pass the test. People are also usually nervous when they are asked to take field sobriety tests, which can affect their performance. In addition, conditions beside the road where the test is administered can affect a person’s performance. Weather conditions, other cars driving past, poor lighting, and uneven ground can all affect performance.

To account for these variables, officers must follow NHTSA protocol. Violations of protocol lend to an unreliable and possibly invalid FST. For example, the officer may not have explained the test properly. The officer may have chosen a poor site to have the test performed. The officer may prematurely terminate the test. The officer may have judged the test unreasonably. The officer may have made a determination that is scientifically or medically unreliable. The officer may not have accounted for individual circumstances on the part of the participant. The challenges to FSTs are widely varied.

There are also legal ways to fight the admissibility of the HGN test. In this test, the officer will have a suspect follow a stimulus, such as a lighted pen, with his or her eyes and look for a nystagmus, or involuntary jerking, which alcohol is known to cause. The HGN is not admissible in Pennsylvania courts although police are permitted to use the test to establish probable cause to arrest.

It is important to carefully examine FST evidence. In many—if not most—instances, police officers do not administer the test in full compliance with NHTSA guidelines. Cross-examining officers with their own training manuals frequently exposes their lack of knowledge and skill in conducting these tests. At trial, all of these factors must be fully explored so that a judge and/or jury understand the fallibility of FSTs.

Most importantly, contact Fairlie & Lippy, P.C. if you have any questions. Remember, a consultation with our Pennsylvania DUI attorneys is always free of charge. As PA DUI lawyers, we have extensive experience in evaluating FSTs conducted in Montgomery County, Bucks County and surrounding communities.

  • Burns, M., & Moskowitz, H. (1977) Psychophysical tests for DWI arrest. Final Report, DOT-HS-802-424, NHTSA.
  • Cole, S., & Nowaczyk, R. (1994) Field Sobriety Tests: Are They Designed for Failure? Perceptual and Motor Skills, Department of Psychology, Clemson University
  • Rubenzer, S. (2007) The Standardized Field Sobriety Tests: A Review of Scientific and Legal Issues. American Psychology-Law Society.
  • Tharp, V., Burns, M., & Moskowitz, H. (1981) Development and field test of psychophysical tests for DWI arrests. Final Report, DOT-HS-805-864, NHTSA.
  • Stuster, J., & Burns, M. (1998). Validation of the Standardized Field Sobriety Test battery at BACs below .10 percent. Washington DC: U.S. Department of Transportation, National Highway Traffic Safety Administration (DOT-HS-808-839).

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