It is not uncommon for a Minnesota police officer to ask a driver to exit a vehicle if he or she suspects the person of intoxication. The officer might also ask a driver to take a horizontal gaze nystagmus test, which is a specialized eye test used to determine if there is probable cause to make an arrest. Someone who receives a failing score on this test could wind up facing DUI charges in court.
Humans have a maximum peripheral vision point. When tracking an object left to right or vertically using eyes only and not the head, the eyeballs will begin to shake or move erratically before reaching this point if the person in question is intoxicated. A police officer who is administering a horizontal gaze nystagmus test is closely monitoring the eyeballs of the test taker to observe whether they exhibit any degree of erratic movement at strategic points throughout the test.
Medical conditions or injuries can make the test unreliable
At best, a horizontal gaze nystagmus test is only accurate a little more than 75% of the time. There are also numerous medical conditions, eye problems or injuries that impede a person’s ability to do well, which can skew test results. In fact, many people have challenged the results of such tests when facing DUI charges in court.
A Minnesota police officer knows what types of conditions can interfere with the reliability of a horizontal gaze nystagmus test and should inquire as to whether a driver has any such condition or injury. It is also possible that a person can have an undiagnosed neurological condition that would affect test results. It is a good idea for any person who is facing DUI charges in this state after failing a horizontal gaze nystagmus test to seek legal consultation with an experienced criminal defense attorney before heading to court.