Flashing a Light in Someone's Eye During an HGN Test: Understanding the Procedure and Potential Issues
The horizontal gaze nystagmus (HGN) test is a standardized field sobriety test (SFST) used by law enforcement to assess the potential impairment of a driver suspected of driving under the influence (DUI) of alcohol or drugs. This test involves observing involuntary jerking movements of the eyes (nystagmus) as the suspect follows a stimulus, often a penlight, with their eyes. However, the proper administration of the HGN test is crucial, and improperly flashing a light in someone's eye can lead to inaccurate results and legal challenges. This article will delve into the correct procedure and address potential concerns surrounding the use of a light source during this crucial test.
What is the HGN Test and How is it Administered?
The HGN test is based on the principle that alcohol and certain drugs affect the central nervous system, resulting in observable nystagmus. The officer observes three primary clues:
- Lack of Smooth Pursuit: As the suspect follows the stimulus, their eyes should move smoothly. Jerky movements indicate a potential problem.
- Distinct Nystagmus at Maximum Deviation: When the eyes are held at their maximum deviation (looking as far to the side as possible), involuntary jerking should be apparent.
- Onset of Nystagmus Prior to 45 Degrees: Nystagmus beginning before the eyes reach a 45-degree angle of deviation is another key indicator.
The officer slowly moves the stimulus horizontally, instructing the suspect to follow it with their eyes only. The light source is crucial for this process, providing a clear and consistent visual target. The crucial part is the controlled, slow movement of the light – not the intensity or type of light itself. Incorrect use of the light can significantly impact the accuracy of the test.
How Can Improper Use of a Light Source Affect the HGN Test?
Improper use of the light source during the HGN test can invalidate the results. Several issues can arise:
- Light Too Bright/Close: An overly bright light or one positioned too close to the suspect's eyes can cause discomfort and involuntary eye movements, leading to a false positive. The suspect might involuntarily blink or squint, obscuring the observation of nystagmus.
- Light Movement Too Fast or Erratic: If the light is moved too quickly or erratically, it can interfere with the subject's ability to follow it smoothly, resulting in inaccurate assessment of smooth pursuit and potentially leading to a false positive.
- Inconsistent Lighting Conditions: Changes in ambient light or inconsistent light source intensity can also affect the accuracy of the observations. The testing environment should be well-lit but not overly bright.
- Lack of Training: If the officer administering the test is not properly trained in the correct technique of light usage and interpretation of nystagmus, this will directly impact the results' validity.
Is Flashing a Light in Someone's Eye During the HGN Test Acceptable Practice?
No, flashing a light repeatedly or rapidly in someone's eyes is not an acceptable practice during the HGN test. This technique is not part of the standardized procedure and can significantly distort the results. The light should be moved slowly and steadily, providing a consistent visual stimulus. Rapid flashing can cause temporary visual disruption and involuntary eye movements, leading to inaccurate interpretations.
What are the Legal Ramifications of an Improperly Administered HGN Test?
An improperly administered HGN test, including the improper use of a light source, can lead to the exclusion of the test results in court. A skilled attorney can challenge the admissibility of the test if they can demonstrate that the procedure deviated from established standards, affecting its reliability. This can significantly weaken the prosecution's case.
This information is for educational purposes only and should not be considered legal advice. Always consult with a legal professional for advice regarding specific legal matters.
