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  • Writer's pictureBrian Foley

Houston DWI Lawyer - Field Sobriety Testing

Standardized field sobriety tests (SFSTs) are a set of three roadside tests that officers use during a DWI investigation to determine if someone is driving under the influence. While SFSTs are used by Houston officers, they were developed in the 1970s and have since undergone minimal changes. These tests are standardized in that they were created based on studies conducted by the government to associate motor performance on tests with blood and breath alcohol levels. Officers look for "clues" during the tests that indicate whether or not someone is intoxicated and use this information to form an opinion about their level of intoxication.

The first test that officers typically administer is the Horizontal Gaze Nystagmus (HGN), which is an eye test that checks for involuntary eye jerking. The officer holds a stimulus, like a pen or finger, 12-15 inches away from the person's nose and slightly elevated, and asks them to follow the stimulus with their eyes only, keeping their head still. The theory behind this test is that alcohol first inhibits fine motor function, which includes the muscles controlling the eyes. There are six clues (three per eye) that officers look for during the HGN, including whether the eyes track smoothly from left to right and back, if there's eye jerking when looking all the way to the right or left, and whether there's nystagmus before the stimulus is extended to a 45-degree angle. While officers often consider the HGN the most reliable test, it's also the least verifiable and should be performed by an expert or a doctor as things other than alcohol can cause nystagmus.

The second test officers typically perform is the 9 Step Walk and Turn, which is a walking test that requires the person to take nine steps down an imaginary line, touching heel to toe on each step, turn around using a series of small steps, and take nine steps back. The officer looks for clues such as stepping out of the instructional position, starting too soon, stopping while walking, failing to touch heel to toe on every step, taking the wrong number of steps, making an improper turn, using arms for balance, and stepping off the line. If the officer observes two or more of these clues, the person is considered intoxicated. Interestingly, many clues are never mentioned during the instruction phase.

The final test officers usually administer is the One Leg Stand, which is a balancing test that requires the person to lift one foot approximately six inches off the ground, point their toe, and count in the following manner 1001, 1002, 1003, and so on until the officer tells them to stop. The officer looks for clues such as swaying while balancing, putting the foot down, using arms for balance, and hopping. Hopping is considered the most damaging clue to observe in this test, as almost every person accused of DWI puts their foot down prior to the 30 seconds that the officer is testing.

Brian Foley is a distinguished lawyer in the Texas legal community who holds the coveted Board Certification in Criminal Law, a mark of excellence achieved by only 7,200 of the 110,000 licensed lawyers in Texas. His outstanding accomplishments and vast experience as a Felony Chief Prosecutor in Harris County, where he was in charge of a third of all cases filed in Houston ranging from Capital Murder to Driving While Intoxicated, make him an exceptional choice to handle your legal matters. With his wealth of knowledge, expertise, and experience in criminal law, he is well-equipped to provide you with the best legal representation and help you achieve a positive outcome in your case. Don't hesitate to call Brian Foley, and let his experience work for you.

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