Field Sobriety Testing

In the 1970’s, the National Highway Traffic Safety Administration funded research to identify techniques that police officers could rapidly employee on the roadside which would provide empirically reliable evidence of whether a driver was driving while intoxicated. The researchers originally tested 6 different field tests. However, they later concluded that a three test battery would provide the most accurate results. Those three tests were the Horizontal Gaze Nystagmus, the Walk and Turn and the One-Leg Stand. These three standardized test are universally taught at law enforcement academies and are used in almost every jurisdiction. Judicial officers are likely to hear testimony regarding them in the vast majority of DUI trials. A general familiarity with tests and the science behind them will help judicial officers navigate this are of the law.

Validation Studies

W. M. Bosker, et al, “A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid,” Psychopharmacology (2012)  This study addresses the effectiveness of SFSTs to detect cannabis intoxication. 

Steven J. Rubenzer, “The Standardized Field Sobriety Tests: A Review of Scientific and Legal Issues,” Law and Human Behavior, Vol. 32, No. 4 (Aug., 2008)  This study addresses the effectiveness of SFSTs to detect cannabis intoxication.

K. Papafotiou, “An evaluation of the sensitivity of the Standardized Field Sobriety Tests (SFSTs) to detect impairment due to marijuana intoxication,” Psychopharmacology (2005) 180: 107–114 This study addresses the effectiveness of SFSTs to detect cannabis intoxication.

Stuster, Jack, et al. Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent: Final Report (1998). – “The results of this study provide clear evidence of the validity of the Standardized Field Sobriety Test Battery to discriminate above or below 0.08 percent BAC. Further, study results strongly suggest that the SFSTs also accurately discriminate above or below 0.04 percent BAC.”

Burns, Marcelline et al., A Florida Validation Study of the Standardized Field Sobriety Test (S.F.S.T.) Battery (1997) – “The data obtained during this study demonstrate that 95% of the officers' decisions to arrest drivers were correct decisions. Furthermore, 82% of their decisions to release drivers were correct. It is concluded that the SFST's not only aid police officers in meeting their responsibility to remove alcohol impaired drivers from the roadway, they also protect the rights of the unimpaired driver. These data validate the SFST's as used in the State of Florida by Pinellas County Sheriffs deputies who have been trained under NHTSA guidelines. SFST validity now has been demonstrated in Florida, California (1997) and Colorado (1995).”

Other Resources on SFST
Horizontal Gaze Nystagmus—The Science and the Law: A Resource Guide for Judges, Prosecutors and Law Enforcement. NHTSA - This guide is designed especially to assist judges, prosecutors and law enforcement personnel in gaining a basic understanding of HGN, its correlation to alcohol and certain other drugs, other types of nystagmus, the HGN test’s scientific validity and reliability, its admissibility in other jurisdictions, and the purposes for which it may be introduced.

Evaluation of the Effects of SFST Training on Impaired Driving Enforcement, NHTSA, 2011 - As a result of SFST training, officers reported increased confidence in performing DWI-related activities com­pared to pre-SFST training levels.

The Robustness of the Horizontal Gaze Nystagmus (HGN) Test, NHTSA, 2007 - Three experiments examined the effects of procedural variations in administration of the HGN test. Variations in stimulus speed and elevation, and distance of the stimulus from the suspect’s face were examined in a laboratory experiment. A second experiment conducted in training workshops varied the participants’ positions (standing, sitting, lying down). The third experiment examined HGN in participants who have functional vision in only one eye. The data demonstrate the validity of the HGN test with both standard and varied testing procedures. The variations did not alter the occurrence of, or the observations of, HGN.

Admissibility of Horizontal Gaze Nystagmus: Targeting Hardcore Impaired Drivers, American Prosecutors Research Institute, May 2003 - This resource details apparent advantages of the HGN test and suggests why it should be admissible in court.

Development of a Standardized Field Sobriety Test (SFST) Training Management System, NHTSA, November 2001 - This report presents the results of a study conducted for the National Highway Traffic Safety Administration to develop a model system for managing Standardized Field Sobriety Test (SFST) training within a state. The report is presented in three sections. This brief Introduction discusses the historical context of the study and presents the objectives of the research. The second section of the report describes the tasks that were performed and presents study results. The third section discusses the specifications of a computerized model system for tracking SFST training.

Psychophysical Tests for DWI Arrest, NHTSA, 1977 - On the basis of preliminary investigations, six tests were chosen for an evaluation study. Ten officers administered the 6-test battery to 238 participants who were light, moderate and heavy drinkers. Placebo or alcohol treatments produced BACs in the range 0 - .15%. The police officers scored the performance of each test on a 1-10 scale, and on the basis of the entire battery judged whether the person should be arrested or released. All of the 6 tests were found to be alcohol sensitive, and the officers made correct arrest/release decisions for 76% of the participants. Data analysis led to recommendations of a “best” reduced battery of tests which includes examination of balance (One-Leg Stand) and walking (Walk-and-Turn), as well as the jerking nystagmus movement of the eyes (Alcohol Gaze Nystagmus).

Court Cases
State v. Homan, 89 Ohio St.3d 421 (2000)
Ohio Supreme Court held that any variation in the use of NHTSA standardized field sobriety tests make the result complete unreliable as it relates to probable cause, a much lower standard than proof beyond a reasonable doubt needed for conviction.

The Homan court stated: “It is well established that in field sobriety testing even minor deviations from the standardized procedures can severely bias the results.” The court reasoned, to “the small margins of error that characterize field sobriety tests, making strict compliance critical.” The court found that “when field sobriety testing is conducted in the manner that departs from established methods and procedures, the results are inherently unreliable.”

City of West Bend v. Wilkeus, 04-1871 (2005)
The Wisconsin Court of Appeals stated: “Other than the bare assertion that the recommended standardized tests are both scientifically reliable and valid, the record contains no indication that they are based on science. Any scientific explanation for why the standardized procedures yield any particular result is completely absent. Standardization may lead to reliability in the sense that where examiners look for the same “clues” to shape their observations of the subject, their observations are likely to be more similar. Similarity does not equate to more correct observations, however. The mere fact that the NHTSA studies attempted to quantify the reliability of the field sobriety tests in predicting unlawful [blood alcohol content] does not convert all of the observations of a person’s performance into scientific evidence.”

State v. Meador, Florida (1996)

United States v. Horn, 185 F. Supp. 2d 530 (D. Md. 2002).

NCSC Library Resources:
Available from the NCSC Library by emailing Joan Cochet at jcochet@ncsc.org.
Dietrich, James J. Horizontal Gaze Nystagmus: The Science and the Law: A Resource Guide for Judges, Prosecutors and Law Enforcement. Washington, D.C.: American Prosecutors Research Institute, National Traffic Law Center, 1999. (Available in the NCSC library: KF2231 Z95 H67 1999).