Daytona Beach DUI Defense Lawyer
Retired Homicide Detective. Former DUI Investigator. Trial Attorney.
One of the most common questions people ask after a DUI arrest is:
“Can the HGN test be wrong?”
The short answer is:
Absolutely.
Like any field sobriety exercise, the Horizontal Gaze Nystagmus Test, commonly known as the HGN Test, is not perfect.
The test depends on:
- Human observation
- Officer training
- Proper administration
- Correct interpretation
Mistakes can happen.
Medical conditions can affect results.
Environmental factors can affect observations.
And officers can reach incorrect conclusions.
For these reasons, HGN evidence is frequently challenged in Florida DUI cases.
At the Law Offices of Patrick J. McGeehan, P.A., we carefully analyze HGN testing procedures in every DUI case.
Before becoming a lawyer, Patrick served as a police officer, DUI investigator, traffic homicide investigator, police instructor, and homicide detective.
He administered field sobriety exercises and later learned how to challenge them in court.
Today, he uses that experience to defend individuals charged with DUI throughout Daytona Beach, Volusia County, Flagler County, and throughout Florida.
What Is The HGN Test?
The Horizontal Gaze Nystagmus Test is a field sobriety exercise used by police officers during DUI investigations.
The officer asks a driver to follow an object with their eyes while keeping their head still.
The officer then observes eye movements and looks for what are commonly called “clues.”
According to DUI training materials, certain eye movements may be associated with alcohol consumption.
However, the officer is not measuring alcohol concentration.
The officer is observing and interpreting behavior.
That distinction is important.
Related Page:
What Is HGN?
Why The HGN Test Can Be Wrong
Many people assume the HGN test works like a breathalyzer.
It does not.
A breath test generates a numerical result.
The HGN test relies upon human observation.
Human observation is subject to error.
That alone creates the possibility of mistakes.
Officer Error Happens
The HGN test must be administered according to standardized procedures.
Potential errors include:
Moving The Stimulus Too Fast
Moving The Stimulus Too Slowly
Improper Positioning
Incorrect Timing
Failure To Follow Training Standards
Misinterpreting Eye Movements
Any of these errors may affect the reliability of the results.
Officers Can See What They Expect To See
One issue that frequently arises in DUI litigation is confirmation bias.
An officer who already suspects intoxication may unconsciously interpret observations in a way that confirms that belief.
This is not necessarily dishonesty.
It is simply a human tendency.
The problem is that it can affect conclusions.
Medical Conditions Can Produce HGN
One of the biggest weaknesses in the HGN test is that alcohol is not the only thing that can affect eye movements.
Medical conditions may include:
- Vertigo
- Inner ear disorders
- Concussions
- Brain injuries
- Neurological disorders
- Eye disorders
- Vestibular conditions
An officer may not know about these conditions during a roadside investigation.
As a result, medical explanations may be overlooked.
Fatigue Can Mimic Signs Of Impairment
Many DUI arrests occur late at night.
People stopped during these hours are often:
- Exhausted
- Sleep deprived
- Working long shifts
- Traveling long distances
Fatigue may affect appearance, concentration, and eye behavior.
These factors can influence an officer’s interpretation of HGN observations.
Prescription Medications Can Affect HGN
Many legal medications may affect eye movements.
Examples include medications prescribed for:
- Anxiety
- Sleep disorders
- Pain management
- Muscle spasms
The existence of HGN clues does not automatically establish alcohol impairment.
Related Page:
DUI With Prescription Drugs
Marijuana Cases Create Additional Issues
Marijuana DUI investigations frequently involve HGN discussions.
Questions often arise regarding:
- Whether marijuana causes HGN
- Whether other substances were involved
- Whether the officer properly interpreted observations
Drug-related DUI cases often present scientific questions that are far more complicated than many people realize.
Related Page:
Marijuana DUI Defense
Environmental Conditions Can Affect Testing
The HGN test is often administered roadside.
That environment is far from ideal.
Potential distractions include:
- Flashing emergency lights
- Passing traffic
- Rain
- Wind
- Noise
- Headlights
These factors may interfere with the testing process.
Body Camera Footage Often Reveals Problems
One of the most common surprises in DUI cases occurs when body camera footage is reviewed.
Police reports often contain statements such as:
“The defendant displayed six out of six clues.”
The video may tell a different story.
Questions often include:
- Did the officer follow proper procedures?
- Were instructions clear?
- Was the stimulus positioned correctly?
- Were distractions present?
Video evidence frequently becomes one of the most important parts of the defense.
The HGN Test Does Not Measure BAC
This point cannot be emphasized enough.
The HGN test does not tell an officer:
- Blood alcohol concentration
- Breath alcohol concentration
- Number of drinks consumed
The officer simply observes eye movements and forms an opinion.
That opinion may be challenged.
The HGN Test Does Not Determine Guilt
Even if an officer believes HGN clues are present, the State must still prove:
- Driving or actual physical control
- Impairment
- Proper police procedures
- Reliable evidence
The HGN test is only one piece of a much larger puzzle.
Why DUI Lawyers Challenge HGN Evidence
HGN evidence is challenged every day in Florida courts.
Common reasons include:
Improper Administration
Medical Conditions
Prescription Medications
Officer Training Deficiencies
Environmental Distractions
Incomplete Documentation
Constitutional Violations
Officer Credibility Issues
The existence of HGN clues does not automatically mean the officer is correct.
HGN Evidence And Jury Trials
Many jurors initially assume the HGN test is scientific proof of intoxication.
Cross-examination often reveals a different reality.
Jurors frequently learn:
- The officer is not a doctor.
- The officer is not an ophthalmologist.
- The officer is not a neurologist.
- The officer is interpreting observations.
Understanding those limitations often changes how jurors evaluate the evidence.
Related Page:
DUI Jury Trial Lawyer
HGN Evidence And Motions To Suppress
Sometimes the issue is not whether the HGN test was accurate.
Sometimes the issue is whether the officer should have been conducting the investigation at all.
Potential issues may include:
- Illegal traffic stops
- Improper checkpoints
- Unlawful detentions
- Lack of reasonable suspicion
Related Page:
Motion To Suppress DUI Evidence
Frequently Asked Questions
Can The HGN Test Be Wrong?
Yes.
Officer error, medical conditions, medications, and environmental factors may affect results.
Can A Sober Person Display HGN?
Potentially.
Certain medical conditions and other factors may affect eye movements.
Does HGN Prove Intoxication?
No.
The test does not directly measure alcohol concentration.
Can HGN Evidence Be Challenged?
Absolutely.
HGN evidence is frequently challenged in DUI cases.
Can A DUI Case Be Won Even If The Officer Claims Six Out Of Six Clues?
Yes.
The HGN test is only one piece of evidence in the case.
Why Clients Choose Patrick J. McGeehan
Many attorneys handle DUI cases.
Few have administered HGN testing before becoming lawyers.
Patrick’s background includes:
- Former DUI Investigator
- Police Officer
- Police Instructor
- Retired Traffic Homicide Investigator
- Retired Homicide Detective
- Trial Attorney
Most attorneys learn HGN testing from reports and courtroom testimony.
Patrick administered field sobriety exercises himself and later learned how to challenge them.
That experience provides valuable insight when evaluating HGN evidence.
A Career Dedicated To Challenging The Evidence
Every DUI case raises important questions.
Was the HGN test administered correctly?
Was the officer properly trained?
Could medical conditions explain the observations?
Can the State prove impairment beyond a reasonable doubt?
Patrick has spent decades evaluating evidence and asking those questions.
As a police officer, DUI investigator, traffic homicide investigator, homicide detective, and trial attorney, he has devoted his career to uncovering facts and protecting the rights of the accused.
That same commitment guides every DUI defense today.
Contact A Daytona Beach DUI Defense Lawyer
If your DUI case involves HGN evidence, do not assume the officer’s conclusions are correct.
The test can be wrong.
The observations can be challenged.
The evidence matters.
The defense matters.
Contact the Law Offices of Patrick J. McGeehan, P.A. today to schedule a consultation and learn how an experienced Daytona Beach DUI lawyer can evaluate HGN evidence and help protect your rights and your future.
Resources:
Leaving the Scene of an Accident With a Death
Fatal Crash Investigations in Florida