What Advanced SFST Training Taught Me About Roadside DUI Tests

Most people have seen field sobriety tests on television. An officer moves a pen in front of someone’s eyes, asks them to walk a straight line, and then has them stand on one leg. It looks simple. It also looks like something you either “pass” or “fail.”

After spending three intensive days in Atlanta learning how standardized field sobriety tests are supposed to be administered, I can tell you there is much more to it.

The course covered the National Highway Traffic Safety Administration’s procedures for administering and scoring the standardized field sobriety tests, commonly called SFSTs. We participated in two alcohol workshops, completed hands-on practical exercises, passed a proficiency examination, and studied the research commonly offered in support of these tests.

We also learned how to challenge SFST evidence in court.

My biggest takeaway was straightforward: these tests are called “standardized” for a reason. The instructions, demonstrations, testing conditions, timing, and scoring all matter. When an officer changes the test, rushes it, gives incomplete instructions, counts something that is not a recognized clue, or administers it under poor conditions, the resulting evidence deserves careful scrutiny.

What Are the Standardized Field Sobriety Tests?

The NHTSA battery consists of three tests:

• The Horizontal Gaze Nystagmus test, or HGN
• The Walk-and-Turn test
• The One-Leg Stand test

These tests are intended to help officers make roadside arrest decisions. They are not the same as a breath or blood test, and they do not directly measure how safely a person was driving.

Officers are trained to look for specific, defined observations—usually called “clues”—during each test. Although people commonly talk about “passing” or “failing” field sobriety tests, that language oversimplifies what is supposed to occur. The officer should administer the test according to the standardized procedure, observe only the recognized clues, and score those clues according to the training manual.

That sounds orderly on paper. A roadside investigation at night can be a very different story.

Proper Administration Involves More Than Saying, “Walk the Line”

The training drove home how detailed the proper procedures are.

Before administering the tests, an officer should consider whether the person has injuries, medical conditions, balance problems, vision issues, or other limitations that could affect performance. Testing conditions matter as well. The original research contemplated a dry, hard, level, non-slippery surface under reasonably safe conditions.

That is not always what we see on body-camera video.

A person may be standing beside a busy road with traffic passing a few feet away. The pavement may be sloped, cracked, wet, covered in gravel, or poorly lit. The person may be exhausted, frightened, cold, or dealing with an old knee, back, or inner-ear problem. None of those circumstances automatically proves that the testing is invalid, but they may provide an innocent explanation for what the officer interpreted as impairment.

The instructions and demonstrations also matter. The officer is supposed to explain the test, demonstrate the required movements, and make sure the person understands before beginning. If the officer leaves something out and then counts the resulting mistake against the driver, that is a problem.

The HGN Test Requires Precise Timing and Positioning

During the HGN test, an officer asks the person to follow a stimulus—often a finger, pen, or small light—with their eyes while keeping their head still. The officer looks for particular types of involuntary eye movement.

Proper administration requires attention to details such as:

• The distance and height of the stimulus
• The speed at which it moves
• The amount of time it is held in certain positions
• Whether the eyes track equally
• Whether the pupils are equal in size
• Whether resting nystagmus is present
• Whether the person has a relevant eye or medical condition

The stimulus generally should be held approximately 12 to 15 inches from the center of the person’s face and slightly above eye level. Different portions of the test require different movement speeds and holding times.

Those details are not trivia. Move the stimulus too quickly and the officer may not be administering the test that was taught. Skip the medical checks and an important alternative explanation may be missed. Conduct the test from a poor angle and the officer’s ability to observe both eyes may be compromised.

That is why video matters. An officer may write “six of six clues” in a report, but the footage may tell us whether the officer actually performed all the required passes, used the proper timing, and had a clear view of the person’s eyes.

The Walk-and-Turn and One-Leg Stand Are More Specific Than They Look

The Walk-and-Turn is not simply a request to walk down a line. It includes an instructional position, a series of heel-to-toe steps, a particular type of turn, and a return sequence.

Officers are trained to score particular clues. The definitions matter.

For example, merely swaying during the instructions is not necessarily the same as breaking the heel-to-toe position. A small heel-to-toe gap may fall within the allowed tolerance. A “step off the line” should mean the foot actually comes off the line—not that part of a shoe briefly touches its edge. Raising an arm should not be counted unless it meets the trained standard.

The One-Leg Stand has similar details. The officer must give and demonstrate the instructions, time the test appropriately, and distinguish among swaying, hopping, briefly moving a foot, and actually putting the foot down.

In court, one of the most important questions is whether the officer scored the test according to the manual or according to a looser personal definition.

What the Alcohol Workshops Added

Reading the NHTSA procedures is one thing. Administering the tests to real people is another.

During two alcohol workshops, we had the opportunity to observe and administer SFSTs under controlled conditions. That experience illustrated how much judgment can enter the process. Different people can consume alcohol and present very differently. Some may perform portions of the tests surprisingly well. Others may display issues that are subtle or difficult to score consistently.

The workshops also emphasized the importance of maintaining objectivity. Once an officer believes a driver is impaired, there is a risk that every movement will be viewed through that lens. A wobble becomes a clue. A request for clarification becomes an inability to follow directions. Nervousness becomes impairment.

A standardized scoring system is supposed to limit that subjectivity—but only if the officer follows it.

The Proficiency Examination Changed How I Review DUI Videos

We did not receive a certificate simply for sitting through lectures. We had to demonstrate the tests and pass a proficiency examination.

That experience gave me a better appreciation for the number of steps an officer is expected to remember. It also sharpened the way I review body-camera and dash-camera footage.

I am not just asking whether my client stumbled. I am asking:

• Did the officer screen for medical or physical limitations?
• Were the instructions complete?
• Was each test demonstrated correctly?
• Did the officer confirm that the instructions were understood?
• Were the surface and lighting suitable?
• Was the HGN stimulus positioned and moved correctly?
• Did the officer use the required timing?
• Did the officer count only recognized clues?
• Does the written report accurately describe what the video shows?

Sometimes the officer follows the training closely. Sometimes the video reveals significant departures. Either way, the defense should know the difference.

What Does the Research Actually Support?

A major portion of the course focused on the studies commonly used to support SFST evidence. This was where the training became particularly valuable.

The point was not that every study is worthless or that SFSTs can never provide useful information. The more measured—and more important—point is that the studies have limitations that are often left out when a prosecutor or witness quotes an overall “accuracy rate.”

Some of the concerns include the following.

The Studies Often Evaluated Arrest Decisions, Not Driving Ability

Several well-known studies examined whether officers made the “correct” decision to arrest or release a driver based on the SFST battery and other observations. That is different from proving that one test, standing alone, accurately measures driving impairment.

Driving is a complicated activity involving attention, judgment, perception, reaction time, and motor skills. Walking heel-to-toe beside the road is not driving a car.

A test may assist an officer in deciding whether to investigate further without being a scientifically precise measure of whether a person was incapable of safely operating a vehicle.

The Study Populations Matter

Some validation studies included a large percentage of participants who were already over the applicable alcohol limit, with average alcohol concentrations well above the borderline range.

That creates a base-rate problem. If most people in a study are over the limit, an officer can achieve an impressive overall accuracy rate simply by classifying most people as over the limit. The headline number may sound strong while revealing much less about how well the test distinguishes a sober or borderline driver.

For someone accused of DUI, the important question is not merely how many decisions were correct overall. It is also how frequently sober people or people below the threshold were incorrectly classified.

The Full Battery Is Not the Same as One Test

In several field studies, officers used all three SFSTs along with observations such as driving behavior, speech, appearance, admissions, and the odor of alcohol.

When those ingredients are combined, it can be difficult to determine how much predictive value came from HGN, how much came from the physical tests, and how much came from everything else the officer observed.

A study of the entire decision-making process does not necessarily validate HGN as a stand-alone measure of a particular alcohol concentration or of driving impairment.

Reliability Between Officers Is Important

A reliable test should produce reasonably consistent results when it is administered and scored by different qualified people under the same conditions.

That is especially important with field sobriety testing because small scoring decisions can change the officer’s conclusion. If one officer counts a movement as a clue and another trained officer does not, that disagreement matters.

The studies do not always provide the kind of test-retest and interrater reliability information we would want before treating a roadside observation as precise science.

Can Sober People Look Impaired on These Tests?

One especially interesting study asked officers to watch videos of 21 completely sober people performing field sobriety exercises and more familiar, everyday tasks. The officers were considerably more likely to describe the participants as having had too much to drink after watching the field sobriety exercises.

That study has limitations of its own. It was small, did not include HGN, and included exercises beyond the current three-test standardized battery. It should not be treated as the final word.

Still, it demonstrates an important point: unfamiliar balance and coordination exercises can make sober people look impaired, especially when the viewer is expecting the exercises to reveal impairment.

A Recent Court’s Treatment of HGN Evidence

The course materials also included a recent Georgia trial-court order examining proposed expert testimony about HGN under the Daubert standard for scientific evidence.

The court did not rule that alcohol cannot cause nystagmus. It accepted that alcohol can affect gaze-holding ability. However, based on the evidence presented in those cases, the court rejected broader expert opinions that HGN could reliably establish a particular BAC level or driver impairment. The court permitted properly administered HGN results only as circumstantial evidence of alcohol consumption.

That order is from a Georgia trial court. It is not controlling law in Alabama, and its ruling depends on the evidence and arguments presented in those particular cases. But it illustrates why courts and defense attorneys should examine the underlying methodology instead of treating the word “scientific” as the end of the discussion.

What This Means in an Alabama DUI Case

An officer’s notation that a driver “showed clues” on the SFSTs does not end the case.

The defense can compare the officer’s conduct against the training manual, examine whether the testing conditions were appropriate, identify innocent explanations for the person’s performance, and question whether the officer’s conclusions go beyond what the tests can actually establish.

At trial, the goal is not to pretend that alcohol never affects balance, coordination, or eye movement. It plainly can. The goal is to insist on a fair and complete picture:

• What did the officer actually observe?
• Was the test administered correctly?
• Were the clues scored according to the manual?
• What else could explain the observations?
• What does the research support?
• Is the officer describing a limited screening tool or presenting it as something more conclusive?

Those are very different questions from simply asking whether someone “failed.”

Arrested for DUI in Auburn, Opelika, or Lee County?

A DUI arrest can affect your driver’s license, employment, education, professional opportunities, and reputation. The roadside tests may feel like only a few minutes from a much longer encounter, but they can become a central part of the State’s case.

My recent SFST training strengthened my ability to evaluate that evidence from both sides: how the tests are supposed to be administered and how their limitations can be exposed in court.

If you have been arrested for DUI in Auburn, Opelika, or elsewhere in Lee County, contact Vaughn Defense at (334) 232-9392 to schedule a confidential consultation. The sooner the evidence can be preserved and reviewed, the sooner we can begin identifying the issues that may matter to your defense.

This article provides general information and is not legal advice. Every case depends on its particular facts, evidence, and applicable law.