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Horizontal Gaze Nystagmus Test Evidence in Colorado

The Framework under Campbell v. People

June 2020

This article examines the standards for evaluating horizontal gaze nystagmus test evidence in trial courts and administrative proceedings for license revocation. It looks at the effects of the 2019 ruling in Campbell v. People.

In 1975 the National Highway Traffic Safety Administration (NHTSA) developed standard field sobriety tests (SFSTs) for law enforcement to determine alcohol driving impairment,1 and law enforcement implemented the SFSTs in 1981. Law enforcement employs three SFSTs: horizontal gaze nystagmus (HGN), walk and turn (W&T), and one leg stand (OLS). There are other tests, such as the Romberg test, but NHTSA has not sanctioned them.2

The science supporting the use of SFSTs to determine alcohol impairment is reasonably reliable3 yet still somewhat controversial.4 Many courts admit all SFSTs, with some taking judicial notice of their scientific reliability and noting their acceptance in the scientific community for alcohol impairment. But the admissibility of the science related to the HGN test has met varying results.5 As noted by the Maryland Court of Special Appeals:

The majority of foreign jurisdictions that have addressed the issue have held that the test for HGN is a scientific test. Most of those few states that have held that it is not a scientific test opine that its admissibility depends upon a lesser standard because it is a mere field test and, thus, is admissible without a scientific foundation. Thus, in both the states holding that the HGN test is a scientific test (the majority) and those states holding that it is only a field test, it is, nevertheless, admissible so long as certain predicates are satisfied.6

Colorado joined the majority in 2019 when the Colorado Supreme Court held in Campbell v. People that the HGN test is scientific evidence under CRE 702.7 Post-Campbell, courts can expect to receive motions in limine seeking prevention of prosecution evidence relating to HGN evidence. This article examines the new standards for evaluating HGN issues applicable in Colorado trial courts and administrative proceedings.

The Campbell Framework

In Campbell, the defense argued during pretrial proceedings that the prosecution intended to have the police officer who conducted the SFSTs, including the HGN test, testify as a lay witness. Campbell argued that the SFSTs comprised “a specialized area of knowledge,” and therefore the officer should be permitted to testify only about his observations and not be allowed to offer “any opinions that stem from those observations that are based on this specialized knowledge that the officer had.”8 The trial court did not make a formal finding during pretrial motions but indicated it would consider an objection at the appropriate time during trial, and it noted that there could be testimony by an officer on roadside maneuvers that would require expert opinion.9

At trial, the police officer testified extensively about his training and experience on conducting SFSTs, noting his estimated 700 DUI investigations over his 15-year career as a police officer, which included “wet lab” training.10 The officer explained the HGN test and described the six clues, three separate clues in each eye, that he would look for when performing the test. The officer testified that he had conducted the SFSTs on the defendant and gave specific testimony about how he performed the test in accordance with the standards, and what an officer looks for during each step of the test as the officer observes the subject’s eyes tracking the stimulus. The officer’s testimony detailed where the stimulus is held, how it is moved, and what signs demonstrate each clue.11

Campbell was convicted of driving while ability impaired and appealed the conviction to the Arapahoe County District Court. He argued that the trial court allowed impermissible lay witness testimony from the officer regarding the HGN test. The district court affirmed the trial court and held that the officer had developed his opinions on the clues seen during the HGN testing by watching Campbell’s eye movement, which the court opined was something that any ordinary citizen could do. Thus, the testimony was admissible as lay witness testimony under CRE 701.12

In its analysis on appeal, the Colorado Supreme Court noted that Rule 701 states that a lay witness’s testimony in the form of opinions or inference is limited to those that are “(a) rationally based on the perception of the witness, (b) helpful to a clear understanding of the witness’ testimony or the determination of a fact in issue, and (c) not based on scientific, technical, or other specialized knowledge within the scope of Rule 702.” On the other hand, Rule 702 provides that “[i]f scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise.”13

In analyzing the officer’s testimony on the HGN test under the principles and definitions in Rules 701 and 702, the Court first noted that the officer’s testimony was not the type that could be offered without specialized experience, knowledge, or training.14 Instead, according to the officer’s own testimony at trial, it was his extensive training and experience that qualified him to perform the test, which underscored that the testimony was not lay witness testimony.15 The Court found that a lay person without training would not be familiar with the principles of the HGN test and would not be able to explain the administration and interpretation of that test.16 Therefore, the Court found that the trial court had abused its discretion when it admitted the officer’s testimony as lay testimony and did not require the officer to be qualified as an expert witness under Rule 702.

In analyzing the error, the Court noted the plethora of evidence supporting the jury’s determination that Campbell was impaired. This evidence included the results of the failed W&T and OLS tests; the three small bottles of alcohol, including one opened, on the floor of Campbell’s car; the two breath tests that revealed a breath alcohol content of .07 and .086; Campbell’s admission that he had consumed alcohol; and Campbell’s lack of denial that he was impaired when the officer administered the sobriety and breath tests.17 The overwhelming evidence supported the jury’s determination that Campbell drove while his ability was impaired by alcohol. The Court found that any error in admitting the officer’s testimony as lay witness testimony had not affected the defendant’s substantial rights and was thus harmless.

Campbell is distinguishable from an earlier 2019 Colorado Supreme Court decision in People v. Kubuugu, where the Court found that the trial court’s error in admitting a deputy’s testimony on metabolized alcohol as lay testimony was not harmless.18

Campbell is most akin to the decision in Schultz v. State, where the Maryland Court of Special Appeals referenced drawbacks of the HGN test:

One of the test’s shortcomings is that the officer administering the test may not be properly trained to understand all aspects of the test and to produce results as accurately as the NHTSA manual suggests. . . .

. . .

To demonstrate a proper foundation, an officer must show that he is trained in the particular procedure, that he is certified in the administration of the procedure, and that the procedure was properly administered.19

Campbell’s Effect in Trial Court Proceedings

Campbell’s effect on trial proceedings differs depending on whether the SFST evidence at issue is considered during trial or at a preliminary motion hearing.

During Trial

The Campbell decision signals challenges to an officer’s qualifications as an expert in cases where HGN testing was performed. In Colorado, an officer must meet the test enunciated in People v. Shreck, where the Colorado Supreme Court followed the Daubert 20 standard and held that in making decisions on admissibility of expert testimony, a court must find on the record that the testimony is appropriate because it is (1) regarding scientific principles that are reasonably reliable, (2) helpful to the jury, (3) probative under CRE 403, and (4) given by a qualified expert or witness qualified to make opinions on the issues.21

Other states have seen appeals on whether their version of Rule 702 requires proof that HGN testing is reliable. In North Carolina, another Daubert analysis state, the court of appeals held in State v. Younts that a law enforcement officer trained to administer the HGN test may properly testify to the results of a test he or she administered without any determination by the trial court that HGN testing is scientifically reliable, and that N.C. Gen. Stat. § 8C-1, Rule 702(a) does not require the State to lay a foundation for the reliability of the HGN testing before a qualified expert may testify about the results of an HGN test.22 The court also noted that the North Carolina General Assembly changed the Rule 702(a) requirement for expert qualification to state:

(a) If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training or education may testify thereto in the form of an opinion, or otherwise, if all of the following apply:

(1) The testimony is based upon sufficient facts or data.

(2) The testimony is the product of reliable principles and methods.

(3) The witness has applied the principles and methods reliably to the facts of the case.23

The court pointed out that a “strict reading of Rule 702”24 would suggest that the trial court erred by admitting HGN testimony without taking judicial notice of or inquiring into the reliability of the HGN test. However, it analyzed the adoption of Rule 702(a) and its previous ruling in State v. Goodwin to find that no Daubert reliability review is required for HGN testing because of the special admissibility language in Rule 702(a).25

The North Carolina court’s analysis of the reliability review under its Rule 702 does not appear to be the analysis that Colorado courts would apply under Shreck and subsequent cases.26 In a pre-trial Shreck hearing in Colorado, the prosecution can expect to be taxed with a showing as one point of proof the reliability of the HGN test method, and the trial judge has the gatekeeping function on this point as well as the others under Shreck.

Campbell has changed how trial judges must analyze the testimony of law enforcement and drug recognition evaluators in alcohol impaired driving cases. Such witnesses who testify at trial in these cases concerning HGN testing will not be permitted to testify as lay witnesses because the standard for admissibility of this testimony has changed to that of scientific evidence under Rule 702. Judges will now have to be convinced that the witnesses have the scientific expertise to opine about the HGN test.

Preliminary Hearings

Other jurisdictions have dealt with the question of HGN test admissibility at preliminary hearings. Notably, in Commonwealth v. Weaver, the Pennsylvania Superior Court considered the trial court’s denial of appellant’s suppression motion.27 Appellant argued that a trooper’s probable cause finding was subject to challenge because it included HGN test results with no proper foundation established for the scientific evidence to be admitted.28 The court noted that probable cause to arrest may be supported by evidence that is inadmissible at trial, and the probable cause determination is made in the context of facts known to the police officer.29

Weaver relied on US Supreme Court precedent on evaluating probable cause determinations in Brinegar v. United States, where the Court clarified that the “criterion of admissibility in evidence, to prove the accused’s guilt” should not be applied to “the facts relied upon to show probable cause.”30 The Wisconsin Court of Appeals followed this reasoning as well. It quoted Brinegar to find that, in a pretrial suppression hearing, a court properly relied on the arresting officer’s recorded statement that he stopped defendant because he twice observed his vehicle cross the center line, which was hearsay.31 Thus, courts have made it clear that there is a distinction between the rules applicable to proceedings to determine probable cause for arrest and search, and those governing the criminal trial itself.

Campbell and Express Consent Hearings

The rules of evidence applicable in civil cases generally apply to hearings conducted pursuant to the Colorado Administrative Procedures Act (APA) under CRS § 24-4-105(7),32 and it has been held that to the extent they are consistent, both the judicial review provisions in Colorado’s express consent statute, CRS § 42-2-126,33 and the APA provisions govern the procedures applicable to administrative hearings.34

However, hearing procedures under Colorado’s express consent statute differ from those under the APA generally. The express consent statute specifies that the Colorado Department of Revenue (Department) and the hearing officer conducting the hearing “shall consider all relevant evidence at the hearing, including the testimony of any law enforcement officer and the reports of any law enforcement officer that are submitted to the department.”35 Thus, the express consent statute is inconsistent with the APA in that all information submitted by an officer, including details of the officer’s HGN impairment examination submitted to the Department, other field sobriety tests, and his or her testimony on those tests are to be considered. The standard for examining the officer’s probable cause determination is not too different from a court’s analysis of HGN results at preliminary hearings: the “criterion of admissibility in evidence, to prove the accused’s guilt” should not be applied to “the facts relied upon to show probable cause.”36 Further, the express consent statute specifies that “the hearing officer shall have authority to . . . [r]eceive and consider any relevant evidence necessary to properly perform the hearing officer’s duties as required by this section.”37

Thus, in administrative proceedings under CRS § 42-2-126 for license revocation, a revocation element may be established by hearsay evidence alone without violating due process if such evidence is sufficiently reliable and trustworthy and possesses probative value commonly accepted by reasonable and prudent persons.38 It is not a Shreck or Daubert analysis, but an analysis of whether the process protects the “procedure’s integrity and fundamental fairness.”39 The licensee has the right to present evidence rebutting any element of the prima facie case shown by the officer.40 A driver’s license revocation hearing is an administrative hearing not governed by the strict rules of evidence and procedure that pertain to a criminal action.41 The statute evidences a legislative intent to treat separately the administrative and criminal consequences of driving under the influence. Thus, to avoid interpreting the statute in a way that defeats the legislative intent, the hearing officer must give effect to the ordinary meaning of the language and read the provisions as a whole, “construing each provision consistently and in harmony with the overall statutory design, if possible.”42 The obligation to give a licensee a fair hearing does not include the same formalities that adhere to a criminal trial.

The level of scrutiny at an administrative license revocation hearing is also unique. For example, at a preliminary hearing, a judge may not engage in credibility determinations unless the testimony is incredible as a matter of law.43 An express consent hearing has a broader scope,44 and neither the burden of proof nor the strict application of the rules of evidence required in criminal hearings applies. Thus, Campbell does not apply to the admission of the HGN results in administrative license revocation proceedings.

What about Drugged Driving Cases?

The use of HGN tests in drugged driving cases raises issues beyond those addressed in Campbell. Campbell involved an alcohol driving case, but what approach will the Colorado Supreme Court take in a drugged driving case where law enforcement uses SFSTs? Will it make a difference if the law enforcement officer is a drug recognition evaluator or an ARIDE (Advanced Roadsides Impairment Detection Enforcement) officer?45 Does special training in drug detection automatically allow the admission of HGN test results because of the underlying scientific training? Will this place a new burden on law enforcement officers by requiring them to have additional training?

HGN clues indicating impairment are not observed with all drug use. The HGN test is valid for central nervous system depressant drugs, inhalants, and PCP (phencyclidine), because they affect the same neural centers as alcohol.46 However, cannabis does not produce similar HGN clues.47 The HGN test along with other SFSTs was addressed in Massachusetts v. Gerhardt, a recent marijuana driving case in which the state’s supreme court held that law enforcement officers may testify as to their observations related to conducting SFSTs, including the HGN test, but may not offer an opinion as to whether those observations equate to driving impairment.48


Post Campbell, Colorado trial courts can expect pretrial motions on HGN test evidence, and trial judges must make specific findings under Shreck on the admissibility of HGN test results. Practitioners should note the limitation of the ruling as it applies to preliminary hearings and administrative license revocation hearings. But unresolved questions remain about how Campbell will apply to drugged driving cases, so practitioners should remain alert for further developments in this regard.

Mary A. Celeste served on the Denver County Court bench from 2000 through 2015. She was the presiding judge in 2009–10 and the cofounder of the Denver County Court Sobriety Court. Celeste is currently a law school professor teaching marijuana and the law at California Western School of Law, and she performs research for the NHTSA and the National Opinion Research Center on the prosecution of drugged driving cases. She has written many articles and is a national speaker on the topics of marijuana, marijuana and drug impaired driving, drugged driving, and specialty courts. Julie J. Van Dyne is an administrative hearings officer with the Colorado Department of Revenue. Previously, she served as a prosecutor in Colorado and the Commonwealth of the Northern Marina Islands, and as an administrative hearings officer in Texas and Colorado. The views expressed in this article are the authors’ own and do not necessarily represent the views of the Colorado Department of Revenue or any other state agency. Coordinating Editor: Judge Adam Espinosa.

Related Topics


1. NHTSA, Validation of the Standardized Field Sobriety Test Battery at BACs Below 0.10 Percent (Aug. 1998),

2. The Romberg test requires subjects to stand erect with their feet together and eyes closed, and sometimes perform the finger-to-nose test.

3. Stuster, “Validation of the standardized field sobriety test battery at 0.08% blood alcohol concentration,” Hum Factors 48:608-14 (Fall 2006).

4. NHTSA, Horizontal Gaze Nystagmus: The Science and the Law,

5. Rubenzer, “The standardized field sobriety tests: a review of scientific and legal issues,” 32:4 Law and Human Behavior 293–313 (2008); Busloff, “Can Your Eyes Be Used Against You—The Use of the Horizontal Gaze Nystagmus Test in the Courtroom,” 84 J. Crim. L. & Criminology 216–33 (Spring 1993). See also Cowan and Jaffee, Proof and Disproof of Alcohol-Induced Driving Impairment Through Evidence of Observable Intoxication, 9 Am.Jur. Proof of Facts 3d 459 (Lawyers Coop. Publ’g 1990); Taylor and Oberman, Drunk Driving Defense § 4.4.5 (Wolters Kluwer 3d ed. Supp. 1994); Rouleau, Unreliability of the Horizontal Gaze Nystagmus Test, 4 Am. Jur. Proof of Facts 3d 439 (Lawyers Coop. Publ’g 1989); Erwin, Defense of Drunk Driving Cases (Matthew Bender 3d ed. 1985); State v. Superior Court, 718 P.2d 17 appendices A and B (Ariz. 1986).

6. Schultz v. State, 664 A.2d 60, 63 (Md.App. 1995).

7. Campbell v. People, 443 P.3d 72, 74 (Colo. 2019).

8. Id.

9. Id.

10. Id. Wet labs are officer alcohol testing workshops where volunteers consume alcohol and have their intake monitored. The volunteers are then taken through the SFSTs by officers. The results of these SFTS are analyzed in conjunction with the subjects’ tracked alcohol consumption.

11. Id. at 74–75.

12. Id. at 75.

13. Id. at 76.

14. Id. at 76.

15. Id. at 76–77.

16. Id. at 77.

17. Id. at 77–78.

18. People v. Kubuugu, 433 P.3d 1214 (Colo. 2019).

19. Schultz, 664 A.2d 60, 62 (quoting Busloff, supra note 5).

20. Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993).

21. People v. Shreck, 22 P.3d 68, 77 (Colo. 2001).

22. State v. Younts, 803 S.E.2d 641 (N.C.App. 2017).

23. Id. at 645–46 (citing 2011 N.C. Sess. Laws ch. 283, §1.3 (emphasis added)).

24. Id. at 648.

25. Id. at 646 (citing State v. Goodwin, 786 S.E.2d 34, 38 (N.C.App. 2016), aff’d in part and rev’d in part by 800 S.E. 2d 47 (N.C. 2017)).

26. Shreck, 22 P.3d at 77; Kinny v. Keith, 128 P.3d 297, 314 (Colo.App. 2005) (noting that when deciding the admissibility of expert testimony, a court must make findings on the record under Shreck that the testimony is reasonably reliable, along the other Shreck test elements); People v. Jimenez, 217 P.3d 841, 866 (Colo.App. 2008) (citing Shreck and People v. Ramirez, 155 P.3d 371, 378 (Colo. 2005) (“To determine reliability, the court considers whether the scientific principles underlying the testimony are reasonably reliable” along with whether the expert is qualified)).

27. Commonwealth v. Weaver, 76 A.3d 562 (Pa.Super.Ct. 2013).

28. Id. at 567 (citing Brinegar v. United States, 338 U.S. 160 (1949), and Commonwealth v. Devlin, 289 A.2d 237 (Pa.Super.Ct. 1972)).

29. Id.

30. Brinegar, 338 U.S. at 172.

31. State v. Zamzow, 874 N.W.2d 328, 331 (Wis.App. 2015).

32. Dep’t of Higher Educ. v. Singh, 939 P.2d 491 (Colo.App. 1997).

33. CRS § 42-2-126(10)(a).

34. Meyer v. State, 143 P.3d 1181, 1186 (Colo.App. 2006). See also CRS § 42-2-126(11); Gilbert v. Julian, 230 P.3d 1218, 1221 (Colo.App. 2009).

35. CRS § 42-2-126(8)(c).

36. Brinegar, 338 U.S. at 172.

37. CRS § 42-2-126(8)(d)(IV).

38. Colo. Dep’t of Revenue v. Kirke, 743 P.2d 16, 21 (Colo. 1987). See also Partridge v. State, 895 P.2d 1183 (Colo.App. 1995); Colo. Div. of Revenue v. Lounsbury, 743 P.2d 23 (Colo. 1987); Charnes v. Olona, 743 P.2d 36 (Colo. 1987); Heller v. Vasquez, 743 P.2d 34 (Colo. 1987); and CRS § 24-4-105(7).

39. Id. at 21 (citing Richardson v. Perales, 402 U.S. 389, 410 (1971) (upholding the use of hearsay reports in Social Security disability hearings)).

40. Id. at 22.

41. Campbell v. Dep’t of Revenue, 491 P.2d 1385, 1388 (Colo. 1971).

42. Whitaker v. People, 48 P.3d 555, 558 (Colo. 2002). See also Francen v. Colo. Dep’t of Revenue, 328 P.3d 111, 115 (Colo. 2014).

43. People v. Smith, 597 P.2d 204, 207 (Colo. 1979), overruled on other grounds by People v. Vance, 933 P.2d 576 (Colo. 1997), overruled by Griego v. People, 19 P.3d 1 (Colo. 2001); Hunter v. Dist. Court, 543 P.2d 1265, 1268 (Colo. 1975); People v. Ramirez, 30 P.3d 807, 809 (Colo. 2001) (Testimony is “incredible as a matter of law” if it is “in conflict with nature or fully established or conceded facts. It is testimony as to facts which the witness physically could not have observed or events that could not have happened under the laws of nature.”).

44. A licensee may request the issuance of a subpoena to support a defense, and the Department has an obligation to grant a subpoena as part of its statutory obligation to provide a meaningful opportunity for a fair hearing. Gilbert, 230 P.3d 1218. A licensee may not be denied the opportunity to present rebuttal evidence challenging breath test results. Mameda v. Colo. Dep’t of Revenue, 698 P.2d 277, 279 (Colo.App. 1985).

45. See

46. Nat’l Inst. on Drug Abuse, Prescription CNS Depressants,; Adler and Burns, Drug Recognition Expert (DRE) Validation Study: Final Report to Arizona Governor’s Officer of Highway Safety (1994); Smith et al., “Drug recognition expert evaluations made using limited data,” 130 Forensic Science Int’l 167–73 (Dec. 2002).

47. See Porath-Waller and Beirness, “An Examination of the Validity of the Standardized Field Sobriety Test in Detecting Drug Impairment Using Data from the Drug Evaluation and Classification Program,” 15 Traffic Injury Prevention 125 (Canadian Centre on Substance Abuse 2014),

48. Commonwealth v. Gerhardt, 81 N.E.3d 751 (Mass. 2017). See also Celeste, “The Impact of the Gerhardt Decision on Marijuana Driving Cases,” vol. 53, iss. 4 Court Review at 170 (American Judges Ass’n 2017),