The Horizontal Gaze Nystagmus or HGN test is used by officers during an investigation for suspicion of driving while impaired (DWI) or driving under the influence (DUI). The officer will hold a flashlight behind his or her fingertip, pen tip, or penlight while instructing the suspect to follow the tip of their item while he or she moves it horizontally from left to right. An officer conducting the HGN test looks for jerking or bouncing of the eye also known as nystagmus during the horizontal movement. A person impaired by alcohol might not be able to control their horizontal eye movements in a smooth and accurate fashion.

Officers are taught to look for six “clues” which is three per eye as to whether a suspect is intoxicated. The officer is trained to look for smooth pursuit of eyes on the horizontal object, maximum deviation jerking or bouncing of the eye or eyes, and prior to 45 degrees there is jerking or bouncing of the eye or eyes. The officer does not need to witness all six “clues” because the training only requires the officer to witness four “clues”. If four “clues” or cues are witnessed by the officer are supposedly an indication of a driver being under the influence of alcohol with a blood alcohol level of 0.08 or higher.

This test is erroneously rated one of the most accurate in conducting a field sobriety test for impairment. If conducted improperly the test will provide a false reading. The test can be affected by the flashing lights of the squad car or the headlights of the passing cars. The test can also be affected by a person’s nerves. Another factor that can affect the test results is the weather and the wind. Further, a recent study from the National Highway Traffic Safety Administration revealed that HGN test has no predictive correlation to a suspect’s blood alcohol level is under or over the legal limit.

This roadside test is often used with other field sobriety tests since most of the time the environment is not perfect to get an accurate result. Most of the field sobriety tests are done on the side of the road where cars are continuing to pass by or there is a possibility of wind or weather conditions affecting the result. Even though the test has been found to be inaccurate it is still used during most DWI or DUI investigations. Your defense lawyer can challenge aspects of the HGN test in pre-trial litigation, implied consent revocation hearings, and trial. The charade of field sobriety testing is just a means to get to the preliminary breath test (PBT) and arrest for a DWI. You can refuse field sobriety testing, including the PBT. If you do that, however, be prepared for the officer to arrest you on suspicion of DWI. Taking the evidentiary breath, blood, or urine test is more important than the roadside field sobriety tests. The evidentiary breath, blood, or urine test is what the cops and prosecutors will use to charge someone with a DWI. Refusing the evidentiary test will result in a Refusal DWI in Minnesota.

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