Top Things That Can Skew Field Sobriety Test Results


Many factors can influence the results of field sobriety testing. In some cases, a knowledgeable DWI attorney can use these things to successfully challenge your dui case.

If you are stopped by a law enforcement officer for a traffic infraction like improper turn or an incomplete stop at a stop sign, you can anticipate getting a ticket. You know the officer will come to your window and ask you for your driver’s license, vehicle registration, and insurance. As he is trained to do, he will observe your behavior, using his sensory input to sniff out suspicious behavior. If the officer finds your behavior abnormal and jittery while avoiding the officer’s gaze, and slurring your speech, especially if they smell alcohol, you can be sure they will ask you if you had been drinking or are driving under the influence of drugs. Regardless of your answer, you will probably be asked to step out of the vehicle to take a field sobriety test. You can refuse, but you cannot refuse to take a breathalyzer test without serious legal consequences. And yet, any number of factors may influence how an individual performs on a field sobriety test. 

Experienced DWI defense attorneys who have handled numerous DUI cases know that field sobriety tests can yield mistaken results. For this reason, it is critical to retain an attorney who can challenge the test results and remove them from evidence at trial if you have been accused of failing a field sobriety test and arrested. At William Proetta Criminal Law, our attorneys can often battle the prosecutor’s drunk driving evidence to ensure our clients are not convicted on a false field sobriety test result. From our local office in Jersey City, we combat DWI charges throughout Hudson County, including in Hoboken, Secaucus, Weehawken, Union City, Kearny, and North Bergen. If you are in need of assistance with a DWI charge, contact us today at (201) 793-8018 or contact us online for a free consultation.

Types of Field Sobriety Testing New Jersey Uses During DWI Arrests

Most officers determine whether a driver is drunk if they fail two of the criteria for passing the field sobriety test. New Jersey uses three types of field sobriety tests: the one-leg stand, the walk and turn, and the horizontal gaze nystagmus test (HGN). All three test a driver’s ability to coordinate their bodily movements by performing balance, coordination, visual tracking, and stability tests. As drivers need to respond physically and mentally to changing road conditions, these tests make sense and the National Highway Traffic and Safety Administration endorses them.

The walk-and-turn test requires the suspect to walk heel to toe for several steps but only upon command. So, if the officer tells the driver to line up their feet on a line, then walk one step, placing the heel to the toe of the back foot, then another, all the way up to 9 steps, the driver must complete that task without falling, hesitating, lifting their arms up from their sides or disobeying the instructions of when to step. Otherwise, they may be deemed intoxicated. And holding one leg up for thirty seconds without falling, hopping, or swaying may be enough to pass the one-leg stand. But even after the test is completed correctly, the driver may still appear intoxicated if they sway or need their arms to balance even when their two feet are on the ground.

The horizontal gaze nystagmus (HGN) test examines the movement of the driver’s pupils. The test assumes that a sober person can follow the movement of an object with their gaze without their pupils moving erratically, up and down or side to side as if the viewer lacks control. When an officer administers the test, they may ask you to follow their finger as they move it in front of your face from one side to the other or at the edge of your direct vision and into the peripheral vision. The driver is instructed to follow the officer’s finger or another object without moving their head. If the pupils twitch, the officer may conclude the driver is likely drunk.

Typically, an officer concludes a driver is intoxicated after administrating any one or all of the three tests. Once the driver is deemed most likely intoxicated, they may be required to take a breathalyzer test. If they blow into the device and it registers their blood alcohol concentration (BAC) at .08% or greater, chances are they are going to be charged with DWI, have their car impounded, and be required to appear in Municipal Court in the town or city where the DWI arrest took place. Even if their BAC is lower than the legal DUI threshold, they may still be charged with impaired or reckless driving. However, the field sobriety tests are often given even in the absence of a breathalyzer test.

Factors That Impact Field Sobriety Test Accuracy

There are a whole host of reasons why someone suspected of driving while intoxicated or under the influence may perform poorly on field sobriety tests. Some of the key factors that can negatively impact field sobriety test performance and skew the results include: medical conditions, environmental factors, injuries, and road conditions.

Medical Conditions Can Skew Field Sobriety Tests

A perfectly sober driver with congenital defects, chronic illness, or injury impairment may fail a sobriety test. For example, a driver who was born with a medical condition that weakened the muscles in one leg may have difficulty balancing on a toe to heel test or leg lift test. Those who suffer from rheumatoid arthritis, hip dysplasia, or knee replacement surgery may likewise fail a sobriety test when they are unable to pass two of the three tests. Moreover, an obese person may not be able to lift their leg or walk in a straight line due to body mechanics and proportion.

Even though the HGN test seems more medically-based, it too does not consider medical conditions that affect vestibular functioning, like vision problems. Those with Parkinson’s Disease, Multiple Sclerosis, Bell’s Palsy, Tourette’s Syndrome, or anxiety disorders may be challenged to keep their pupils from twitching. For example, one of the lasting effects of a serious concussion is the inability to track objects without months of vestibular therapy. Many disorders interfere with successfully completing an HGN test without impairing a driver’s ability to drive safely. Officers unfamiliar with these conditions, especially a new officer, may mistake the symptoms of a disease, medical issue, or injury as drunkenness.

Environment Plays a Part in Poor Performance on Field Sobriety Tests

Medical conditions aside, the environment in which the test is administered may also affect the outcome of the tests. Walking toe to heel on gravel, cracked pavement, or dense, leafy surfaces may cause someone to lose footing. The weather may also cause inaccurate results when a test taker is thrown off balance by wind, rain, or slick roads. And a driver who is stopped at night might look away from the officer’s finger when bright headlights flash in front of their eyes. Even those with light sensitivity or trouble seeing at night  can fail a test from environmental interference.

Issues With Field Sobriety Tests Could Offer Your Best Defense When Charged With DWI in New Jersey

If an officer relies on a field sobriety test to arrest someone for a DWI, they must have legitimate results upon which to base their assessment. An arrest occurs after an officer has probable cause to believe a crime or vehicular infraction has occurred. If they stop a driver for erratic driving, they may suspect the driver is drunk. The field sobriety test is one way to confirm their suspicion. However, if the tests are flawed, the arrest may be challenged for insufficient reasons for a DUI arrest. When this is the best route for getting your DWI charge dismissed, you should enlist the most qualified attorney who has a solid handle on all of the complexities of field sobriety tests, proof used for DWI charges, and ways to challenge these cases.

Contact Our Jersey City Law Office to Speak to a DWI Lawyer Today

William Proetta, one of our founding attorneys, is not only knowledgeable about the complexities and nuances of field sobriety testing, he is legitimately among the select few lawyers certified by the National Transportation Safety Administration in proper administration and evaluation of standardized field sobriety tests. On top of that, his is one of the approximately five attorneys in New Jersey recognized as a DUI Detection and Standard Field Sobriety Testing Instructor by the National Highway Traffic Safety Administration and the International Association of Chiefs of Police. This has allowed Mr. Proetta to achieve countless DWI dismissals in cases across the state of New Jersey, including Hudson County towns like Jersey City, West New York, Guttenberg, and Bayonne.

To discuss your DWI case with a seasoned lawyer free of charge, contact our office now at (201) 793-8018 or contact us online for a free consultation.

With more than a decade of experience defending clients against criminal charges, founding partner William A. Proetta has successfully handled and tried thousands of cases, from DWI to murder. As a New Jersey native, he has focused his career on helping people in the area where he grew up, serving Middlesex, Ocean, Hudson, and Union counties.