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Table 4
Percentage of Drivers Judged Impaired At Different BAC Levels Using a Test Battery Including HGN or HGN Alone

	BAC
	00-.04%	.05-.09%	.10-.15%
Briefly Trained Officers	24%	75%	89%
Fully Trained Officers	8%	52%	100%
HGN only (both groups)	15%	64%	95%

Figures in bold are false positives-drivers who would have been falsely arrested.

2) SFST scoring is potentially biased by the officer's suspicion of intoxication. The SFSTs require subjective judgment to score, as acknowledged by Marcelline Burns,⁶⁸ NHTSA reviewers,⁶⁹ and as indicated by their moderate inter-rater reliability coefficients. An officer could easily decide a WAT turn is improper based, in part, of how the driver smelled and his clarity of speech. When these biases seep in, the test has been contaminated.

3) The SFSTs may be harder than driving. The WAT and OLS are unfamiliar and probably strain many sober peoples' abilities, especially those that are not in good physical condition. To quote the NHTSA student manual, "Tests that are difficult for a sober person to perform have little or no evidentiary value."⁷⁰ A recent survey of British police surgeons found about half expressed concerned about the SFSTs being too difficult or the grading too harsh. Amongst those with advanced credentials (a Diploma of Medical Jurisprudence or Diploma of Forensic Medicine) over 60% of respondents expressed reservations for the Walk and Turn and One Legged Stand.⁷¹

4) Although the SFSTs were not designed as indications of driving impairment and have undergone little validation for this purpose, they are still frequently admitted as evidence for establishing the driver was impaired. The SFSTs were expressly developed and validated to distinguish between BACs of above and below .10%-not driving impairment. Marcellin Burns has emphasized this distinction,⁷² but NHTSA materials⁷³ and court decisions⁷⁴ wrongly equate the two terms. While the SFSTs attempt to gauge BAC, NHTSA plainly states "Impairment varies widely among individuals with the same BAC level."⁷⁵

Only a couple of studies have attempted to correlate SFST scores with driving impairment. In one of the original NHTSA laboratory studies, subjects were tested on both the SFSTs and a divided attention performance test designed to simulate the demands of driving. Each SFST correlated about .30 with the different performance measures. When the results of the tests were combined statistically, the two psychomotor tests (WAT and OLS) carried all the weight-HGN added nothing.⁷⁶ Other NHTSA-associated researchers stated "there is no evidence that the eye movements that constitute Nystagmus seriously impair the visual processes involved in driving or operating a boat."⁷⁷ A third group of NHTSA researchers evaluated dozens of behavioral tests to determine their potential to assess driver impairment and other desired qualities. These authors recommended a completely different battery than the SFSTs,⁷⁸ and the SFSTs received low ratings of relevance to driving skills: HGN received a rating of "0" (zero on a scale of 0-100) for its value in assessing driver impairment, while WAT and OLS received ratings of "40" and "20," respectively.⁷⁹

5) SFSTs, particularly HGN, are more prejudicial than probative on the issue of impairment. When a person suspected of DWI/DUI has difficulty performing a field sobriety test, the jury viewing the performance may logically assume the suspect is drunk. Given the circumstances, this is the natural interpretation. A study published by Cole and Nowacyk⁸⁰ had 21 completely sober people perform the sobriety tests (not including HGN) and other tasks. Police officers perceived 46% of the subjects performing sobriety tests as drunk and worthy of arrest. If prejudicial value = high and probative value = low or medium, then high > low or medium = nonadmissible. Meaney argued that a negative HGN is more probative than a positive finding because "no study suggests the possibility of intoxication without . nystagmus."⁸¹

Conclusion
The SFSTs claim to be standardized and validated psychological tests. The first claim is justified if they are administered, scored, and interpreted in line with NHTSA guidelines. Much more serious questions arise regarding their validation and other psychometric properties. The SFSTs have been evaluated primarily by their proponents and there have been no studies of the SFSTs as a group in either laboratory or field studies by disinterested researchers. Just as important, NHTSA training has not encouraged officers to consider other plausible causes of poor performance, such as anxiety or sleepiness.

The SFSTs have significant limitations as tests that should be understood by those who encounter them in the legal arena. Like most tests, they can be useful, but are also easily abused and misunderstood. Defense attorneys must challenge their empirical bases where they can and expose failures to follow the standardized instructions. More importantly, prosecutors and judges need to critically examine the SFST evidence offered in DUI cases so that innocent people are not wrongly convicted. View sample calculations (.xls file)

Notes.
¹ Marcelline Burns & Herbert Moskowitz, Psychophysiological Tests for DWI Arrest, Final Report, DOT-HS-802-424 (1977). V. Tharp et al., Development and Field Test of Psychophysiological Tests for DWI Arrest, Final Report, DOT-HS-805-864 (1981).

² V. Tharp et al., supra. Theodore E. Anderson et al., Field Evaluation of a Behavioral Test Battery for DWI, DOT-HS-806-475 (1983).

³ William A. Pangman, Horizontal Gaze Nystagmus: Voodoo Science, 2 DWI J.: LAW & SCI. 1 (1987). G. Simpson, Attacking NHTSA's Three-Test Field Sobriety Assessment, 3 DWI J., LAW & SCI., 97. Jonathon D. Cowen & Susannah G. Jaffee, Field Sobriety Tests: The Flimsy Scientific Underpinnings, 5 DWI J.: LAW & SCI. 121 (1990). Mark Rouleau, Unreliability of the Horizontal Gaze Nystagmus Test, 4 AM. JUR. POF 3d 439 (1990). Jonathon D. Cowan & Susannah G. Jaffe, Proof and Disproof of Alcohol-Induced Impairment Though Evidence of Observable Intoxication and Coordination Testing, 9 AM. JUR., POF 3d, 459 (1990). Ronnie M. Cole & Spurgeon N. Cole, New Proof That Field Sobriety Tests Are 'Failure-Designed,' 6 DWI J.: LAW & SCI. 1 (1991). Spurgeon Cole & Ronald H. Nowaczyk, Field Sobriety Tests: Are They Designed for Failure? 79 PERCEP. & MOTOR SKILLS, 99 (1994). Randy T. Leavitt, Horizontal Gaze Nystagmus, 22 Voice for the Defense 17 (1994). Ronald H. Nowaczyk & Spurgeon Cole, Separating Myth From Fact: A Review of Research on the Field Sobriety Tests, XIX THE CHAMPION 40 (1995). Charles R. Honts & Susan L. Amato-Henderson, Horizontal Gaze Nystagmus Test: The State of the Science in 1995, 71 N. DAK. L. REV. 671 (1995). Joseph R. Meaney, Horizontal Gaze Nystagmus: A Closer Look, 36 JURIMETRICS J. 383 (1996).

⁴ Marcelline Burns, First Annual DWI Training Seminar, Houston (2000).

⁵ V. Tharp et al., supra.

⁶ Jack Stuster & Marcelline Burns, Validation of the Standardized Field Sobriety Test Battery at BACs Below .10 Percent, DOT-HS-808-839 6 (1998).

⁷ Marcelline Burns & Ellen W. Anderson, Field Evaluation Study of the Standardized Field Sobriety Test (SFST) Battery (Final Report Submitted to the Colorado DOT, November, 1995).

⁸ Marcelline Burns & Teresa Dioquino, A Florida Validation Study of the Standardized Field Sobriety Test (SFST) Battery, (1997).

⁹ Jack Stuster & Marcelline Burns, supra at 8.

¹⁰ Marcelline Burns & Ellen W. Anderson, supra. Marcelline Burns & Teresa Dioquino, supra. Jack Stuster & Marcelline Burns, supra.

¹¹ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000).

¹² Gregory W. Good & Carol R. Augsburger, Use of Horizontal Gaze Nystagmus as a Part of Roadside Field Sobriety Testing, 63 AMER. J. OPTOMETRY & PHYSIOLOGICAL OPTICS, 467 (1986).

¹³ See Louis M. Hsu, Diagnostic Validity Statistics and the MCMI-III, 14 PSYCH. ASSESS. 410, 410-411 (2002).

¹⁴ A. James McKnight et al, Development of a Standardized Boating Sobriety Test, 31 ACCID. ANAL. & PREV. 147 (1999).

¹⁵ A. James McKnight et al., Sobriety Tests for Low Alcohol Blood Concentrations, 34 ACCID. ANAL. & PREV. 305 (2002).

¹⁶ A. James McKnight et al, Development of a Standardized Boating Sobriety Test, 31 ACCID. ANAL. & PREV. 147, 152 (1999).

¹⁷ A. James McKnight et al., Sobriety Tests for Low Alcohol Blood Concentrations, 34 ACCID. ANAL. & PREV. 305 (2002).

¹⁸ THOMAS D. COOK & DONALD T. CAMPBELL, QUASI-EXPERIMENTATION: DESIGN & ANALYSIS ISSUES FOR FIELD SETTINGS 2-9 (1979).

¹⁹ Id., DONALD T. CAMPBELL & JULIAN C. STANLEY, EXPERIMENTAL AND QUASI-EXPERIMENTAL DESIGNS FOR RESEARCH (1962).

²⁰ See also Phillip E. Price & Spurgeon Cole, NHTSA Field Sobriety Tests: Validation and Invalidation, THE CHAMPION, April (2001).

²¹ Marcelline Burns & Ellen W. Anderson, supra at 17.

²² See also J.L. Booker, End-Position Nystagmus as an Indictor of Ethanol Intoxication, 41 SCI. & JUSTICE 113 (2001).

²³ U.S. v. Horn, 185 F.Supp.2d 530, 558 (D.Md. 2002).

²⁴ Marcelline Burns & Teresa Dioquino, supra at 31.

²⁵ Jack E. Richman & John Jakobowski, The Competency and Accuracy of Policy Academy Recruits in the Use of the Horizontal Gaze Nystagmus Test for Detecting Alcohol Impairment, 47 NEW ENG. J OPTOM. 5 (1994).

²⁶ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000) at VIII-8, VIII-12, VIII-14.

²⁷ ELAZAR J. PEDHAZUR, MULTIPLE REGRESSION IN BEHAVIORAL RESEARCH 147-150 (2nd ed. 1982). JUM C. NUNNALLY & IRA H. BERNSTEIN, PSYCHOMETRIC THEORY 333 (3rd ed.1994).

²⁸ Marcelline Burns & Herbert Moskowitz, Psychophysiological Tests for DWI Arrest, Final Report, DOT-HS-802-424 (1977). V. Tharp et al., supra. A. James McKnight et al., Development of a Standardized Boating Sobriety Test, 31 Accident Analysis and Prevention 147 (1999). A. James McKnight et al., Sobriety Tests for Low Alcohol Blood Concentrations, 34 ACCID. ANAL. & PREV. 305 (2002). See also Antti Penttila & Martti Tenju, Clinical Examination as Medicolegal Proof of Alcohol Intoxication, 16 MED. SCI. LAW (1976) 95. Robert S. Kennedy et al., Indexing Cognitive Tests to Alcohol Dosage and Comparison to Standardized Field Sobriety Tests, 55 J. OF STUDIES ON ALCOHOL 615 (1994).

²⁹ V. Tharp et al., supra at 30, 31.

³⁰ Id. 30.

³¹ Id. 16.

³² Joseph Citron, MD, HGN: How to be Your Own Expert Witness (2002) (unpublished manuscript, http://www.ncdd.com/dsp_bookstore.cfm).

³³ V. Tharp et al., supra at 7.

³⁴ New Hampshire v. Dahood, #96-JT-707 (Concorde District Court, April 2002) at 11. (New Hampshire Supreme Court remanded the case to the Concord District Court to hold an evidentiary hearing and rule whether the HGN test incorporates scientific principles. If so, the court was to make findings as to the reliability of the test under New Hampshire Rule of Evidence 702).

³⁵ J.L. Booker, supra.

³⁶ Schultz v. State, 106 Md.App. 145, 664 A.2d 60 (1995).

³⁷ Daubert v. Merrell Dow Pharmaceuticals, 113 S.Ct. 2786 (1993).

³⁸ U.S. v. Horn, 185 F.Supp.2d 530, 557 (D.Md. 2002).

³⁹ New Hampshire v. Dahood, supra.

⁴⁰ New Hampshire v. Dahood, (No. 99-510, December 20, 2002).

⁴¹ AMERICAN EDUCATION RESEARCH ASSOCIATION, THE AMERICAN PSYCHOLOGICAL ASSOCIATION, AND NATIONAL COUNCIL ON MEASUREMENT IN EDUCATION, STANDARDS FOR EDUCATION AND PSYCHOLOGICAL TESTING (1999).

⁴² NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000) at VIII-3.

⁴³ Emerson v. State, 880 S.W.2d 759 (Tx.Cr.-App., 1994), Homan v. State, 732 N.E.2d 952 (Ohio 2000).

⁴⁴ Crime to Court: Rappin' Up the DUI (instructional video), South Carolina ETV, in cooperation with the South Carolina Criminal Justice Academy, SC Law Enforcement Division (1995). The Truth Is in the Eyes (instructional video) cited in New Hampshire v. Dahood, supra.

⁴⁵ MURIEL D. LEZAK, NEUROPSYCHOLOGICAL ASSESSMENT 139-140 (3rd ed., 1995).

⁴⁶ V. Tharp et al., supra., at 70.

⁴⁷ Id. at 17.

⁴⁸ Tharp, et al., supra, at 83.

⁴⁹ Phillip B. Price, Sr., Fear and Sobriety Testing (2000) (unpublished manuscript, available from Mr. Price's office, 217 Randolph Avenue, Huntsville, AL 35801, 256-536-6000, dwilawyer @aol.com).

⁵⁰ JUM C. NUNNALLY & IRA H. BERNSTEIN, PSYCHOMETRIC THEORY 265 (3rd ed. 1994). ⁵¹ K.J. Snapper et al., An Assessment of Behavioral Tests to Detect Impaired Drivers, Final Report, DOT-HS-806-211, (1981) at 3-34 to 3-37.

⁵² V. Tharp et al., supra at 32, 35. Figures are cited for Session 1 for interrater reliability, and for same observers for test-retest reliability. ⁵³ Id. at 34.

⁵⁴ JUM C. NUNNALLY & IRA H. BERNSTEIN, PSYCHOMETRIC THEORY 214 (3rd ed.1994). HOI K. SUEN, PRINCIPLES OF TEST THEORIES 141 (1990).

⁵⁵ Tharp et al., supra at 83.

⁵⁶ LESLIE MOREY, PERSONALITY ASSESSMENT INVENTORY PROFESSIONAL MANUAL (1989).

⁵⁷ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000)

⁵⁸ Improved Sobriety Testing, DOT-HS-806-512 (1984) at 7.

⁵⁹ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000).

⁶⁰ Id. at VIII-12. ⁶¹ Marcelline Burns & Herbert Moskowitz, supra at 41.

⁶² V. Tharp et al., supra at 72.

⁶³ A confidence interval is set using the standard deviation rather than the average deviation. For a normal distribution, the standard deviation equals 1.25332 * average deviation. (see R. J. SENTER, ANALYSIS OF DATA: INTRODUCTORY STATISTICS FOR THE BEHAVIORAL SCIENCES 92 (1969). A 95% confidence interval is set by taking the mean +/- twice the standard deviation.

⁶⁴ V. Tharp et al., supra at 63. ⁶⁵ STEPHEN H. GEHLBACH, INTERPRETING THE MEDICAL LITERATURE 183-185 (4th ed. 2002). Louis M. Hsu, supra. ⁶⁶ Richard P. Compton, Pilot Test of Selected DWI Detection Procedures for Use at Sobriety Checkpoints, National Highway Traffic Safety Administration, DOT-HS-806-724 (1985).

⁶⁷ Three hours of training in administration of HGN may not be atypical-most of the 24 hour NHTSA student course is devoted to topics other than administration of the SFSTs. THE TEXAS A&M UNIVERSITY SYSTEM TEEX - LAW ENFORCEMENT TRAINING DIVISION, TEXAS STANDARDIZED FIELD SOBRIETY TESTING PROGRAM INSTRUCTOR MANUAL (2002).

⁶⁸ Marcelline Burns, supra.

⁶⁹ K.J. Snapper et al., supra.

⁷⁰ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000) at VII-3.

⁷¹ Michael O'Keefe, Drug Driving - Standardized Field Sobriety Tests: A Survey of Police Surgeons in Strathclyde. 8 JOURNAL OF FORENSIC MEDICINE 57, 60-61 (2001).

⁷² Marcelline Burns, supra. ⁷³ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000). Horizontal Gaze Nystagmus: The Science & The Law (A Resource Guide for Judges, Prosecutors, and Law Enforcement), National Highway Transportation Safety Administration, http:/www.ntsa.dot.gov/peopole/injury/nystagmus/hgntxt.html

⁷⁴ State v. Baue, 258 Neb. 968 (2000), U.S. v. Horn, 185 F.Supp.2d 530, 561 (D.Md. 2002).

⁷⁵ NATIONAL HIGHWAY TRAFFIC SAFETY ADM., U.S. DEPT. OF TRANSP., HS 178 R2/00, DWI DETECTION AND STANDARDIZED FIELD SOBRIETY TESTING, STUDENT MANUAL (2000) at VII-6.

⁷⁶ Marcelline Burns & Herbert Moskowitz, supra at 54.

⁷⁷ A. James McKnight et al., Development of a Standardized Boating Sobriety Test, 31 ACCID. ANAL. & PREV. 147 (1999).

⁷⁸ K.J. Snapper et al., supra at 4-2.

⁷⁹ Id. 3-34 to 3-37.

⁸⁰ Spurgeon Cole & Ronald H. Nowaczyk, supra.

⁸¹ Joseph R. Meaney, Horizontal Gaze Nystagmus: A Closer Look, 36 JURIMETRICS J. 383, 406 (1996).

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