What Does "6 of 6 HGN Clues" Actually Mean?
"6 of 6 HGN" is one of the most common phrases in DUI reports. Understanding it requires knowing what the six clues actually are, and whether the standardized examination was performed properly.
One phrase appears repeatedly in DUI reports: "HGN: 6/6 clues."
To someone reading the report, six out of six sounds definitive.
It may even sound like a score showing that the driver "failed" every portion of an eye test.
That is not quite what it means.
Horizontal Gaze Nystagmus (HGN) is one component of the Standardized Field Sobriety Test battery.
The officer is trained to evaluate three specific clues in each eye.
Three clues multiplied by two eyes creates six possible clues.
Understanding those clues, and how they are supposed to be evaluated, is essential before deciding what "6/6" actually tells us.
What Is Horizontal Gaze Nystagmus?
Nystagmus is an involuntary jerking of the eyes.
During an HGN examination, an officer asks the person to follow a stimulus, often a finger, pen, penlight, or similar object, with the eyes while keeping the head still.
The officer moves the stimulus horizontally and observes the eyes.
HGN is not based on whether someone can "follow the pen."
The standardized test is looking for specific eye-movement phenomena.
What Are the Six HGN Clues?
There are three standardized clues for each eye.
1. Lack of Smooth Pursuit
The officer moves the stimulus across the person's field of vision and observes whether the eyes track it smoothly.
If the eye exhibits the type of jerking associated with lack of smooth pursuit, the officer records one clue for that eye.
Both eyes are evaluated.
That creates up to two clues.
2. Distinct and Sustained Nystagmus at Maximum Deviation
The stimulus is moved outward until the eye is at maximum deviation.
The officer then holds the stimulus in that position and observes the eye.
If distinct and sustained nystagmus is present, a clue is recorded.
Again, each eye is evaluated separately.
That creates another two possible clues.
3. Onset of Nystagmus Prior to 45 Degrees
The stimulus is moved slowly from the center toward the side.
The officer watches for the point at which nystagmus begins.
If onset occurs before the eye reaches approximately 45 degrees, the officer records the clue.
Each eye is evaluated.
That creates the final two possible clues.
Add them together:
- 2 lack-of-smooth-pursuit clues
- 2 maximum-deviation clues
- 2 onset-prior-to-45-degree clues
Total: 6 possible HGN clues.
Does 6/6 Mean the Person Was "Extremely Drunk"?
Not by itself.
"6/6" tells the reader that the officer reported observing all three standardized clue types in both eyes.
It is not a direct measurement of alcohol concentration.
It should not be read as: "Six clues equals a particular BAC."
Nor does the number tell us how impaired the person appeared in every other portion of the investigation.
HGN is one piece of evidence.
Administration Is Critical
A report can say "6/6."
The next question is: How were those six clues obtained?
HGN is a standardized examination.
Stimulus movement, timing, positioning, sequence, and observation all matter.
A meaningful review may consider:
- Was the stimulus positioned appropriately?
- Was it kept slightly above eye level?
- Were both eyes visible?
- Were the eyes checked for equal tracking?
- Were other preliminary eye observations conducted?
- Was lack of smooth pursuit checked using appropriate movement?
- Was each eye taken to maximum deviation?
- Was the stimulus held sufficiently at maximum deviation?
- Was onset evaluated using a slow enough movement?
- Was each eye evaluated for each clue?
- Was the test substantially completed?
A finding is only as meaningful as the procedure used to obtain it.
"I Saw Nystagmus" Is Not the Entire Analysis
Nystagmus can have multiple causes.
The HGN examination is used because particular forms of gaze nystagmus are associated with alcohol and certain other drug categories.
But simply observing unusual eye movement does not answer every question.
The officer still has to identify the standardized clue correctly and place it in context with the rest of the investigation.
What About Equal Tracking and Pupil Size?
Officers may conduct preliminary checks before scoring the HGN clues.
Those observations can include things such as equal tracking and pupil appearance.
Those preliminary observations are important.
But they are not additional scored HGN clues.
A person does not have "eight clues" because two preliminary observations were also documented.
The standardized HGN score remains based on the three clue types evaluated in each eye.
Can Body Camera Show HGN?
Sometimes.
But HGN video analysis has limitations.
A body camera may not have the resolution, lighting, angle, or proximity necessary to clearly see subtle nystagmus.
That means video may not always allow a reviewer to independently confirm whether the eye actually jerked.
What video can often show much more clearly is how the test was administered. See body camera vs. police report in a DUI case for a broader look at how video and reports can diverge.
For example:
- How many passes were made?
- How quickly did the stimulus move?
- Was each eye checked?
- Was maximum deviation held?
- Was the onset portion performed slowly?
- Did the officer skip a portion?
That can be extremely important.
HGN and Drug DUI Cases
Another common misunderstanding is that HGN is simply a generic drug-impairment indicator.
It is not.
Different drug categories produce different expected eye findings.
HGN is associated with alcohol and certain drug categories but is not expected merely because any impairing drug was used.
This is particularly important in DRE and cannabis DUI cases.
The claimed eye findings should make sense for the substance or drug category being alleged.
What If HGN Was Done Incorrectly?
A procedural deviation does not automatically mean every observation disappears.
But the nature of the deviation matters.
If the officer moves the stimulus too quickly during a portion that depends on timing, the ability to identify the intended clue may be affected.
If maximum deviation is not held, the officer may not have completed the observation required for that clue.
If onset is not evaluated gradually enough, determining where nystagmus began becomes problematic.
The analysis should therefore focus on the relationship between the procedural error and the conclusion being drawn.
The Bottom Line
When a police report says "6 of 6 HGN clues," it means the officer reported:
- Lack of smooth pursuit in both eyes
- Distinct and sustained nystagmus at maximum deviation in both eyes
- Onset of nystagmus prior to 45 degrees in both eyes
That is useful information.
But it is not the end of the analysis.
The important questions remain:
- Was the test properly administered?
- Were all three clue types actually evaluated in both eyes?
- Does video support the administration described?
- Does the HGN evidence make sense alongside the rest of the investigation?
At Legal Limit Consulting, HGN is reviewed as part of the complete DUI case, not simply accepted or rejected because a report contains the words "6/6."
Because six reported clues only matter if the underlying examination reliably supports them.
This article provides general educational information, not legal advice or an opinion about any specific case. Standards, procedures, and evidentiary rules vary by jurisdiction.
If you are an attorney or individual seeking DUI case review, contact Legal Limit Consulting to discuss the case.