Which eye do you check first for a DUI?

• A. Left
• B. Right
• C. Both
• D. Unknown

Answer: (A)

In the DUI eye test, the key thing you’re looking for is horizontal gaze nystagmus—jerking of the eyes as the gaze moves side to side. The typical procedure starts with the left eye to establish a consistent, systematic observation before moving to the right eye. Beginning with the left eye helps you set a baseline for smooth pursuit and makes it easier to spot any jerking early, especially since you’re often positioned to observe from the subject’s left side. After checking the left eye, you perform the same checks with the right eye to confirm that signs of impairment appear in both eyes and to compare responses. While both eyes should be checked, the standard training often specifies starting with the left eye, which is why that option is identified as the correct first step.