Horizontal Gaze Nystagmus Defense Lawyer in Texas

When a driver is stopped for suspected drunk driving in Texas, law enforcement officers often use a number of field sobriety tests to determine if the driver is actually impaired. One of the most common tests is called the Horizontal Gaze Nystagmus test, or HGN test.

Prosecutors often present HGN results as strong evidence of intoxication, but it's not a perfect test. There are a number of other things that may affect this test, and many of them have nothing to do with intoxication.

If you are facing drunk driving charges, you need a DWI defense attorney who understands what this test is, why it's done, and if something else could have affected the results. A horizontal gaze nystagmus defense lawyer in Texas should be able to do all of that. They can share insight on causes of false positives on a breathalyzer test.

What Is Horizontal Gaze Nystagmus?

Horizontal gaze nystagmus is an involuntary jerking movement of the eyes that might be more noticeable when a person is impaired by alcohol or certain drugs.

During a traffic stop, an officer will generally ask the driver to follow a small object with their eyes while not moving their head. Then, as the police officer moves the object, he or she will look for signs of nystagmus as the eyes move back and forth.

Why Police Use the HGN Test in Texas DWI Investigations

The HGN test is a standardized field sobriety test that is recognized by the National Highway Traffic Safety Administration (NHTSA). Police use the test because they believe that an HGN test performed correctly will help establish probable cause to arrest a driver.

Like breath or blood tests, prosecutors sometimes argue that an HGN test is more reliable than walking or balancing tests. However, there are limitations to all of these tests, and a Fort Worth DWI lawyer can create a defense for them.

Problems With the HGN Test Results

It's very common for Tarrant County courts to hear prosecutors say that HGN results are scientifically sound, but the truth is, a DWI attorney can find issues based on their client's medical history, the way the test was conducted, the environment, and even officer interpretation.

Medical Conditions

Some medical conditions might cause nystagmus even if a person is not intoxicated. Some of these include:

• Neurological disorders

• Inner ear problems

• Eye muscle conditions

• Head injuries

• Certain medications

• Fatigue

• Seizure disorders

Some people also naturally have a slight nystagmus even if they are not impaired.

Improper Test Administration

Another possible criminal defense is to consider how the test was administered. It must be done according to very strict guidelines. Things that might affect the test results include:

• The officer moving the stimulus too quickly

• If the object is held at the wrong distance

• Improper lighting

• Not checking for medical conditions before the test is done

• Not giving clear instructions.

Even a small deviation from the guidelines can make the test inaccurate.

Environmental Factors

There are also roadside conditions to consider. The following can interfere with the testing:

• Flashing police lights

• Passing traffic

• Wind

• Uneven ground

• Poor weather

• Stress and anxiety

A driver standing on the side of a busy road at night may not perform under ideal testing conditions.

Officer Subjectivity

The HGN test is also based on the officer's observations. Unlike a breathalyzer test that shows a number indicating a high blood alcohol concentration, HGN results depend on the officer's opinion on whether or not the eye movement is there. Two officers might interpret the same movement very differently.

Can HGN Results Be Challenged in Criminal Court?

Yes. HGN evidence is often challenged in court. A DWI defense lawyer can challenge the results by looking to make sure the following was true:

• The officer was properly trained

• The test followed NHTSA standards

• Medical conditions never affected the results

• Environmental conditions never interfered

• The officer did not offer exaggerated observations

• The traffic stop itself was lawful

In some cases, improper testing procedures may weaken the prosecution’s evidence significantly.

HGN Evidence Alone May Not Prove Intoxication

Though many prosecutors rely on HGN results, it's important to note that this test, alone, cannot prove intoxication. Usually, an officer who believes someone is over the legal limit will look at a combination of factors in addition to the HGN test including:

• Alleged odor of alcohol

• Slurred speech

• Bloodshot eyes

• Driving behavior

• Breath test results

• Other field sobriety tests

In many Fort Worth DWI cases, an experienced criminal attorneys in Fort Worth may challenge whether the total evidence actually supports impairment beyond a reasonable doubt.

Refusing Field Sobriety Tests in Texas

Texas drivers are generally not legally required to perform field sobriety tests during a traffic stop.

This includes:

• HGN testing

• Walk-and-turn tests

• One-leg stand tests

However, officers may still arrest a driver based on other observations if they suspect impairment.

Drivers should understand that refusing field sobriety tests does not automatically prevent arrest or prosecution.

Why Early Legal Representation Matters

DWI cases move quickly in Texas.

Evidence such as:

• Dash cam footage

• Body camera recordings

• Police reports

• Breath test maintenance records

may become important immediately after arrest.

A defense lawyer may begin investigating potential weaknesses in the case early, including problems involving HGN testing procedures.

Early legal representation may also help drivers protect their driver’s license rights during administrative license suspension proceedings.

Potential Defenses to HGN Evidence

Every DWI case is different, but several common defense strategies may apply to HGN-related evidence.

Possible defenses include:

• Improper officer training

• Failure to follow NHTSA standards

• Medical explanations for nystagmus

• Faulty observations

• Illegal traffic stops

• Unreliable roadside conditions

• Inconsistent police reports

• Contradictory video footage

The strength of these defenses depends heavily on the facts of the case.

Consequences of a Texas DWI Conviction

A DWI conviction in Texas may result in serious penalties, including:

• Jail time

• Fines

• Administrative license revocation

• Occupational license consequences

• Increased insurance costs

• Ignition interlock requirements

• Permanent criminal record

Repeat offenses and cases involving accidents or injuries may lead to even harsher consequences.

Because of these risks, challenging questionable evidence may become extremely important.

Contact a Horizontal Gaze Nystagmus Defense Lawyer in Texas

HGN testing plays a major role in many Texas DWI arrests, but the test is not foolproof. Medical conditions, officer error, environmental factors, and improper testing procedures may all affect the reliability of the results.

Drivers facing DWI charges should not assume that failed field sobriety tests automatically guarantee a conviction.

Sparks Law Firm defends those who are accused of DWI and other criminal offenses throughout the Fort Worth area. A skilled defense attorney can review the circumstances surrounding the traffic stop, evaluate the officer’s testing methods, and identify possible defenses to HGN evidence. Reach out for a free consultation.

When a DWI charge depends heavily on field sobriety testing, experienced legal representation can make a significant difference.