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The Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand are the three standard field sobriety tests. All three were developed by the National Highway Traffic Safety Administration (NHTSA) and are the core roadside tests used to observe suspected impaired drivers. Officers may attempt to conduct other tests, but they are not the core standardized tests developed or adopted by the NHTSA. Whether it is the core three tests, or an additional test performed by the officer, the admissibility or weight to be given to the tests can be challenged.
Horizontal Gaze Nystagmus (HGN)
In the HGN roadside test, the officer moves a pen or light across your field of vision and watches how your eyes follow it. They’re looking for an involuntary jerking, known as nystagmus, at certain points in the movement. While this jerking is present with alcohol or substance use, nystagmus has other causes such as neurological diseases, vascular events, trauma, and inner ear disorders.
Walk-and-Turn
The walk-and-turn involves dividing your attention for an instructional stage and then performing the walk. You must take nine heel-to-toe steps, turn, and then return in the same fashion. The officer scores on your balance, step accuracy, whether you start too soon, and if you are following the instructions provided. For those who naturally have balance issues, this test can be problematic.
One-Leg Stand
The one-leg stand involves raising one foot about six inches off the ground and counting aloud. The officer will look to see if you sway, hop, use your arms for balance, or put your raised foot down. It’s another test that could cause issues for someone with poor balance due to age, medical conditions, or previous injury.
Each of these tests has set protocols that an officer must be trained to follow. If they break away from that, it could provide grounds for the court baring the evidence, or your attorney attacking the weight to be given to the officer’s testimony about their observations.
Even when done correctly, standardized tests are incredibly subjective and rely on an officer’s observations, which are opinion rather than fact. Getting strong DUI defense from the start ensures that you have someone who knows where the weak links are in the prosecution’s case.
Tests That Are Not Standardized
Some officers may ask you to perform other roadside tests; however, those are not standardized and carry less weight in courtroom evidence. An officer may ask you to recite the alphabet, touch your finger to your nose while your head is tipped back, or count backwards, but the NHTSA has not standardized these tests.
Can Non-Standardized Field Sobriety Test Results Be Challenged in Court? Yes, they can, as they are subjective and have long been debated compared to chemical tests, which also have potential to be inaccurate. The Conner Law Firm defends drivers evaluated with standardized field sobriety tests insSt. Clair, Madison, and Monroe Counties, and throughout southern Illinois. Our Founding Attorney, Erin K. Conner, is a former prosecutor who brings that insider knowledge into every case to challenge these tests.
Our guide on Field Sobriety Tests in Illinois: What You Need to Know in Illinois has more information on these roadside tests, including how officers document field sobriety results and how that evidence is used in your case.
Attorney Insight
“”Field sobriety tests look scientific on a police report, but they’re built on an officer’s opinion, and opinions have holes. I spent years watching how these cases get built from the prosecution’s side, and I use that same insider knowledge now to take them apart, missed instructions, bad footing, medical conditions no one accounted for. If your case leans on ‘the officer observed,’ I know exactly where to push.” —Erin K. Conner, Founding Attorney and former Chief of the Criminal Bureau, St. Clair County State’s Attorney’s Office
Why the Details Matter
If you agreed to take roadside tests of any kind, the details of your traffic stop matter tremendously. Each of the standardized tests has a defined procedure, and deviating from it undermines the results. The Conner Law Firm defends drivers evaluated with standardized field sobriety tests in St. Clair, Madison, and Monroe Counties, and throughout southern Illinois. Call us today at (618) 277-2421, or text (314) 944-5553, to get started on your defense.
