State v. Blackwell

Argued before BELL, C.J., HARRELL, GREENE, MURPHY, ADKINS, BARBERA and JOHN C. ELDRIDGE, (Retired, Specially Assigned), JJ.



Paul Benjamin Blackwell, respondent, was convicted of multiple offenses, including driving a vehicle while under the influence of alcohol and driving a vehicle while impaired by alcohol. Blackwell appealed his convictions to the Court of Special Appeals. The intermediate appellate court held that Linger’s testimony about the HGN test constituted expert testimony, the admission of which, without qualification by the trial court, was erroneous and warranted remand for a new trial. The judgment of the Court of Special Appeals was affirmed, emphasizing that the HGN test is a scientific test and that testimony recounting a defendant’s performance on the test is admissible in evidence pursuant to Md. Rule 5-702.


Blackwell was charged with multiple offenses surrounding his driving of a vehicle on the morning of August 17, 2005. The charges included driving a vehicle while under the influence of alcohol, driving a vehicle while impaired by alcohol, driving on a revoked license, and driving without a license. At Blackwell’s trial, before a jury in the Circuit Court for St. Mary’s County, the State’s sole witness was Maryland State Trooper Jeffrey Linger, who stopped the vehicle Blackwell was operating on the morning in question.

Trooper Linger testified that he stopped Blackwell’s vehicle after noticing a non-functioning tail light. Linger also testified that when he approached the vehicle to obtain Blackwell’s identification, he detected an odor of alcohol on Blackwell’s breath. Linger further stated that “[Blackwell's] eyes were glassy, speech was slurred.” The Trooper testified that the horizontal gaze nystagmus test was performed and he described the test, its results, and his conclusions.

EXPERT TESTIMONY ISSUE: Did the Troopers statements during court regarding the HGN constitute expert testimony as to require him to be designated as an expert for the trial?


Nystagmus is the “`rapid involuntary oscillation of the eyeballs.'” HGN is “a lateral or horizontal jerking when the eye gazes to the side.” Although HGN is a natural phenomenon, alcohol magnifies its effects. Because nystagmus becomes more pronounced as the degree of alcohol impairment becomes greater, law enforcement officials have looked to HGN as an indicator of alcohol consumption for several decades.

There are certain guidelines for officers to follow when administering the HGN test:

Stand directly in front of the driver and require the individual to stand at attention, feet together and arms to the side in a well-lit area.

Glasses should be removed to ensure proper observation by the officer; the test should not be administered if contacts are worn.

Next, the officer is to instruct the driver to focus the eyes on an object (in this case, a pen) held fifteen inches from the driver at eye level.

The officer then gradually moves the object, or stimulus, horizontally out of the driver’s field of vision towards the ear and watches the driver’s eyeball to detect involuntary jerking—or nystagmus. The police officer observes:

  1. the inability of each eye to follow movement smoothly (“lack of smooth pursuit”),
  2. conspicuous nystagmus, or jerking, at maximum deviation and
  3. the onset of nystagmus prior to reaching a 45 degree angle in relation to the center point. Proper administration of the HGN test reduces the chance that the nystagmus is attributable to any of several possible other causes mentioned in the cases and medical literature.

The court considered whether the officers’ testimonies constituted lay opinion testimony under Md. Rule 5-701 or expert testimony under Md. Rule 5-702. Rule 5-701 (“Opinion testimony by lay witnesses”) provides:

If the witness is not testifying as an expert, the witness’s testimony in the form of opinions or inferences is limited to those opinions or inferences which are (1) rationally based on the perception of the witness and (2) helpful to a clear understanding of the witness’s testimony or the determination of a fact in issue.

Rule 5-702 (“Testimony by experts”) provides:

Expert testimony may be admitted, in the form of an opinion or otherwise, if the court determines that the testimony will assist the trier of fact to understand the evidence or to determine a fact in issue. In making that determination, the court shall determine (1) whether the witness is qualified as an expert by knowledge, skill, experience, training, or education, (2) the appropriateness of the expert testimony on the particular subject, and (3) whether a sufficient factual basis exists to support the expert testimony.

“Md. Rules 5-701 and 5-702 prohibit the admission as `lay opinion’ of testimony based upon specialized knowledge, skill, experience, training or education.” By permitting testimony based on specialized knowledge, education, or skill under … Md. Rule 5-701, parties may avoid the notice and discovery requirements of our rules and blur the distinction between the two rules.

Trooper Linger’s testimony about Blackwell’s performance on the HGN test constituted expert testimony subject to the strictures of Md. Rule 5-702. Linger reported, among other things, that Blackwell had “lack of smooth pursuit” and “distinct nystagmus at maximum deviation” in each eye. This testimony was not based upon Linger’s general knowledge as a layperson but upon his specialized knowledge and training. To be sure, the HGN test is a scientific test, and a layperson would not necessarily know that “distinct nystagmus at maximum deviation” is an indicator of drunkenness; nor could a layperson take that measurement with any accuracy or reliability.

That the very foundation for the admission of HGN test evidence is premised on specialized knowledge and training reinforces our conclusion that testimony about one’s performance on the test is expert testimony within the purview of Md. Rule 5-702. Generally, pursuant to Rule 5-702, a trial judge must make a number of legal determinations:

First, the trial court must determine whether the evidence to be presented is a proper subject for expert testimony. The standard for relevance under Maryland common law is whether the jury will receive appreciable help from the expert testimony in resolving the issues presented in the case.

Before expert testimony is admitted the court must also determine whether the proposed expert is qualified to testify by virtue of education and experience.

Finally, the proposed expert testimony must be competent, that is, the expert’s conclusions must be based upon a legally sufficient factual foundation.

With respect to the first determination, the State must demonstrate that there is a correlation between alcohol consumption and nystagmus. With respect to the last determination, the State must demonstrate that the HGN test was administered properly, in order to reduce the chance that the observed nystagmus was the result of causes other than alcohol.

The difference between the HGN test and other field-sobriety tests is the ability to interpret the results. Unlike the walk-and-turn test or stand-on-one-foot test in which the failure of which is an obvious indication of loss of coordination and balance (indicating intoxication), the irregular movement is not the common knowledge of a lay person. It takes an expert to interpret the results of the test using specialized knowledge and training. Simply describing the movement of a defendant’s eyes would be meaningless unless explained using that specialized knowledge.

The court found that the testimony of the trooper contained that specific knowledge and training as to require the witness to be identified as an expert. The failure by the prosecution to designate him as an expert was erroneous and the court found that remand was warranted for a new trial.