Horizontal Gaze Nystagmus Testing in DUI Cases

What Is Horizontal Gaze Nystagmus (HGN) Testing?

The Horizontal Gaze Nystagmus (HGN) test is one of the three standardized field sobriety tests used by law enforcement to investigate suspected drunk or drugged driving cases. Nystagmus refers to the rapid, involuntary movement or twitching of the eyes as they follow an object. This phenomenon occurs when the specific gravity of the fluid inside the cochlea—a small organ in the ear—becomes imbalanced due to alcohol consumption.

When blood alcohol levels rise, the fluid in the cochlea affects the eyes' ability to move smoothly. During an HGN test, the officer observes these movements and looks for specific clues to determine if the driver is impaired.

The Three Clues of HGN:

1. Inability to Pursue Smoothly: The eyes cannot smoothly follow the stimulus.
2. Twitching at Maximum Deviation: The eyes wiggle or jerk when turned to their furthest point from the nose.
3. Early Onset of Twitching: Twitching begins before the eyes reach a 45-degree angle from the nose.

Proper Administration of the HGN Test

For the HGN test to be valid, it must be administered according to strict standards outlined in police training manuals. The process typically involves the following steps:

1. Positioning: The officer instructs the driver to stand with feet together and arms at their sides.
2. Instructions: The officer explains how to follow the stimulus (usually a finger, pen, or flashlight) with the eyes only, keeping the head still.
3. Confirmation: The officer confirms understanding by asking, “Do you understand?”
4. Pre-Test Questions: The officer inquires whether the individual is wearing contact lenses or has any conditions affecting their eyes.

Failure to follow these procedures can render the test unreliable and potentially inadmissible in court.

Additional Observations Made During the HGN Test

In addition to the three standardized clues, officers often observe and report on other behaviors during the test. These include:

• Following Instructions: Many individuals naturally move their heads while following an object with their eyes, even though instructed not to. Officers may repeat instructions, noting noncompliance to suggest impairment.
• Balance Issues: Losing balance, swaying, or using arms for stability may also be noted, even though these are not standardized clues.

While these observations are not part of the official criteria for determining impairment, they are often included in the officer’s testimony to strengthen the case for intoxication.

Common Errors in HGN Test Administration

Having evaluated hundreds of cases, it is clear that officers frequently fail to administer the HGN test properly. Common mistakes include:

• Improper Stimulus Placement: Holding the stimulus too high, too low, or too close to the face.
• Rushing the Test: Moving the stimulus too quickly for the eyes to follow properly.
• Lack of Baseline Confirmation: Failing to ask about medical conditions or contact lenses that could affect the results.

Most concerning, improper administration of the HGN test can itself induce nystagmus, leading to false positives that are later used as evidence of intoxication.

The Importance of Legal Representation in HGN Test Cases

An experienced Michigan DUI attorney at the Barone Defense Firm will carefully review the video recording of your roadside test to determine whether the HGN test was administered according to proper protocols. If the officer deviated from their training or failed to follow standardized procedures, your attorney can:

1. Challenge the validity of the test.
2. File motions to suppress the results as evidence.
3. Cross-examine the officer to highlight inconsistencies and procedural errors.

By undermining the reliability of the HGN test, your attorney can weaken the prosecution’s case and improve the likelihood of a favorable outcome.

Why Choose Barone Defense Firm for Your DUI Defense?

With decades of experience, the Barone Defense Firm has a proven track record of challenging field sobriety tests, including HGN. We offer:

• Comprehensive Case Reviews: Examining every detail of your arrest and testing procedures.
• Skilled Cross-Examination: Highlighting officer errors and procedural failures.
• Statewide Representation: Serving clients in Bloomfield Hills, Grand Rapids, Ann Arbor, Troy, and beyond.

Protect Your Rights and Your Future

If you’ve been subjected to an HGN test during a DUI stop, don’t leave your future to chance. Contact the Barone Defense Firm today to schedule a free consultation.

Call 248-306-9158 or contact us online for immediate assistance.

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