I was recently asked about the research supporting the Field Sobriety Tests as the are applied to Ohio.  Perhaps it speaks volumes that the most accessible studies support the State, while contrary studies are not touted.  Nevertheless the below studies are a good place to start and explain what the police rely upon when conducting the tests.  The materials below are taken directly from the 2006 National Highway Transportation Safety Administration manual.

OVERVIEW OF SFST

RESEARCH AND DEVELOPMENT

1. For many years law enforcement officers have utilized field sobriety tests to

determine the impairment of a person’s driving due to alcohol influence. The

performance of the person on those field sobriety tests was used by the officer to

develop probable cause for arrest and as evidence in court. A wide variety of

field sobriety tests existed and there was a need to develop a battery of

standardized valid tests.

2. Beginning in late 1975, extensive scientific research studies were sponsored by

NHTSA through a contract with the Southern California Research Institute

published the following three reports:

o California: 1977 (Lab)

o California: 1981 (Lab and Field)

o Maryland, D.C., V.A., N.C., 1983 (Field)

3. SCRI traveled to law enforcement agencies throughout the United States to

select the most commonly used field sobriety tests. Six tests were used in the

initial stages of this study.

4. Laboratory research indicated that three of these tests, when administered in a

standardized manner, were a highly accurate and reliable battery of tests for

distinguishing BACs above 0.10:

o Horizontal Gaze Nystagmus (HGN)

o Walk-and-Turn (WAT)

o One-Leg Stand (OLS)

5. NHTSA analyzed the laboratory test data and found:

o HGN, by itself, was 77% accurate

o WAT, by itself, was 68% accurate

o OLS, by itself, was 65% accurate

o By combining HGN and WAT an 80% accuracy can be achieved.

6. The final phase of this study was conducted as a field validation.

o Standardized, practical and effective procedures were developed

o The tests were determined to discriminate in the field, as well as in the

laboratory.

7. The three standardized test were found to be highly reliable in identifying

subjects whose BACs were above 0.10. The results of the study unmistakably

validated the SFSTs.

SFST VALIDATION STUDIES

1. Three SFST validation studies were undertaken between 1995 and 1998:

o Colorado - 1995

o Florida - 1997

o San Diego - 1998

2. The Colorado SFST validation study was the first full field study that utilized

law enforcement personnel experienced in the use of SFSTs.

o The initial study utilized only a few experienced officers in DWI

enforcement in both a laboratory setting and field setting.

o Correct arrests decisions were made 93% of the time based on the 3-test

battery (HGN, WAT, OLS). Substantially higher than the initial study

results.

3. The Florida SFST field validation study was undertaken in order to answer

the question of whether SFSTs are valid and reliable indices of the presence

of alcohol when used under present day traffic and law enforcement conditions.

o Correct decisions to arrest were made 95% of the time based on the 3-test

battery (HGN, WAT, OLS).

o This is the third SFST field validation study that has been undertaken.

Each has shown that the SFST 3-test battery is the only scientifically

validated and reliable method for discriminating between impaired and

unimpaired drivers.

4. The San Diego SFST validation field study was undertaken because of the

nationwide trend towards lower the BAC limits to 0.08. The question to be

answered was “does SFST discriminate at BAC’s below 0.10".

o Correct arrest decisions were made 91% of the time based on the 3-test

battery (HGN, WAT, OLS) at the 0.08 level and above.

o The results of this study provide a clear evidence of the validity of the 3-test

battery. To support arrest decisions at above or below 0.08, it strongly

suggests that the SFSTs also accurately discriminate BACs at 0.04 and

above.