December 20, 2014

What Makes "Standardized Field Sobriety Tests" Standardized?

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Throughout the course of this series we've discussed the differences between the FSTs (field sobriety tests) and SFSTs (standardized field sobriety tests). The three SFSTs are the horizontal gaze nystagmus, the walk and turn, and the one leg stand tests. The SFSTs have a level of validity other FSTs do not. "Standardized test" is defined by Wikipedia as "a test that is administered and scored in a consistent, or 'standard', manner." Clearly the goal is consistent and standard administration and evaluation in order to avoid bias and subjective determinations of impairment. The Standardized Field Sobriety Tests, touted by the National Highway Safety and Transportation Administration (NHTSA) and the International Association of the Chiefs of Police (IACP), are good but have their flaws. In this segment, we will look at the studies that make the SFSTs "standardized."

The cornerstone of the standardization is an objective, scientific level of credibility. In order to come into evidence, to be considered in a court of law, it must meet the Kelly-Frye Standard. The Kelly-Frye standard is from Frye v. United States (1923) 293 F.1013, and was adopted by the California Supreme Court in People v. Kelly (1976) 17 Cal.3d 24. The Kelly-Frye standard states that test results entered into evidence must be generally accepted within the relevant portions of the scientific community, and exclude from evidence any test results from scientifically unproven methods. Standardization, and the repeatable results that come with peer reviewed studies, is therefore very important for the credibility, acceptability, and getting the SFST results into evidence.

The SFSTs have peer reviewed studies- as a matter of fact they have three. The three studies are from 1995, 1997 and 1998. The 1995 test was completed out of Colorado, the 1997 test out of Florida, and the 1998 out of our own San Diego. Each one of the studies have a question to answer. Anyone familiar with scientific studies (or politics) also know that studies tend to answer said question in the direction the creator wishes it to. These studies are no different.

In 1995 the Colorado study was intended to answer the question, do experienced officers utilizing the walk and turn, horizontal gaze nystagmus, and one leg stand, in a laboratory and field setting, make correct arrest decisions? The study found that officers using the full battery of three tests made the correct arrest decision 93% of the time.

In 1997, the Florida study was to answer the question, are SFSTs valid and reliable indices for the presence of alcohol when used under present day traffic and law enforcement conditions? The Florida study, not surprisingly, found that the SFST full battery test is the only scientifically validated and reliable method for discriminating between impaired and unimpaired drivers. None of the other field sobriety tests (the handpat, fingercount, romberg, etc.) worked on the same level as the SFSTs. The correct arrest decision was made 95% of the time when all three tests were utilized.

Lastly, the 1998 San Diego study was to exam the new, nationwide blood alcohol content of .08% BAC - dropped from .10%. The question being, could the SFSTs discriminate at BACs less than .10%? The study found the three SFSTs could differentiate, and officers made the correct arrest decision 91% of the time. Interestingly, the study also found that three tests could differentiate to .04% and above.

The San Diego study was the first one to be exclusively a field study- not involving any laboratory testing. However, one of the problems with the study is that it involved experienced officers. It is not known what are the average years of service of the officers that took part in the study, nor what percentage of an average police force have the same level of experience as the officers that took part in the study. A more realistic look at the SFSTs would have examined all officer's arrest decisions, as opposed to just "experienced officers."

An examination of the studies shows that there is an internal bias, and there is room for subjective evaluation. Those will be discussed with each individual SFST, and each test will have their separate blog entry. It is important to note that NHTSA either fully or partially paid for all of the studies.

As a SFST instructor, I know the benefits and detriments of each one of these tests intimately. If done properly, they can be very accurate. However, it is the administration of these tests that are their great downfall in the average DUI arrest scenario. Invariably, officers deliver an abbreviated, or inaccurate SFST battery that leads to biased results. And it is only an experienced, properly trained attorney that can tell the difference. Please contact me here if you wish to have your DUI case evaluated.


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The acronyms DUI, DWI, OMVI and OVI all refer to the same thing: operating a vehicle under the influence of alcohol or drugs. The most commonly used terms are DUI, an acronym for Driving Under the Influence, and DWI, an acronym for Driving While Impaired.
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