Witness Testimony and SFSTs


This is the second of six videos produced by the National Center for State Courts and ABA Judicial Outreach Liaisons, supported by NHTSA, about issues in traffic adjudication. In this video, judges discuss the issues surrounding witness testimony and standardized field sobriety tests.

Related Resources

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 fluidPsychopharmacology (2012). This study addresses the effectiveness of SFSTs to detect cannabis intoxication. 

The Standardized Field Sobriety Tests: A Review of Scientific and Legal IssuesLaw and Human Behavior, Vol. 32, No. 4 (August 2008).

Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent: Final ReportNHTSA (August 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.”

A Florida Validation Study of the Standardized Field Sobriety Test (S.F.S.T.) BatteryFlorida State Safety Office (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).”

Horizontal Gaze Nystagmus—The Science and the Law: A Resource Guide for Judges, Prosecutors and Law EnforcementNHTSA. 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 EnforcementNHTSA (May 2011). As a result of SFST training, officers reported increased confidence in performing DWI-related activities comĀ­pared to pre-SFST training levels.

The Robustness of the Horizontal Gaze Nystagmus (HGN) TestNHTSA (September 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.