H.G.N. is best described as a test used to detect impairment due to which substances?

H.G.N. is best described as a test used to detect impairment due to which substances?

• A. Alcohol only
• B. Drugs only
• C. Horizontal Gaze Nystagmus (a test for detecting drug/alcohol use)
• D. Jumper

Answer: (C)

Horizontal Gaze Nystagmus examines involuntary eye jerks as the eyes track a moving stimulus. When someone is under the influence of alcohol or certain drugs, the brain’s control of eye muscles becomes impaired, causing the eyes to jerk at specific angles that can be observed by an officer. This test is routinely used as part of the field sobriety assessments to indicate impairment from substances, not just one particular drug or alcohol alone. That broader purpose is why it’s described as a test for detecting drug/alcohol use. The other options are narrower or unrelated—focusing only on alcohol, only on drugs, or on something unrelated—whereas HGN is specifically about detecting impairment due to substances that affect the nervous system.

Horizontal Gaze Nystagmus examines involuntary eye jerks as the eyes track a moving stimulus. When someone is under the influence of alcohol or certain drugs, the brain’s control of eye muscles becomes impaired, causing the eyes to jerk at specific angles that can be observed by an officer. This test is routinely used as part of the field sobriety assessments to indicate impairment from substances, not just one particular drug or alcohol alone. That broader purpose is why it’s described as a test for detecting drug/alcohol use. The other options are narrower or unrelated—focusing only on alcohol, only on drugs, or on something unrelated—whereas HGN is specifically about detecting impairment due to substances that affect the nervous system.