Interstate 35 (I-35) is the 9th largest interstate in the United States. It runs north and south from the bottom tip of Laredo, Texas to the very top of Minnesota. In Texas I-35 is commonly known for connecting Austin and San Antonio. While the exact number of DWI arrests along I-35 is not tracked, it is widely known as a hotbed for DWI and other intoxication arrests. I-35 is patrolled by the Texas Department of Transportation and various local law enforcement agencies.
Field Sobriety Exercises in a DWI Arrest
At the crux of a DWI investigation are the Field Sobriety Exercises. Officers have suspects perform these coordination exercises to develop probable cause for an intoxication arrest and prosecutors use the officer’s findings to prove the accused did not have “the normal use of their physical or mental capacities.”
DWI Field Sobriety Instructions and Signs of Intoxication
Background and Faults of the DWI Field Sobriety Exercises
Three studies contributed to the development of sobriety tests used today: 1977 Psychophysical Tests for DWI Arrest; 1981 Development and Field Test of Psychophysical Tests for DWI Arrests; and 1983 Field Evaluation of a Behavioral Test Battery for DWI. These studies were all conducted in a lab (as opposed to real life, field conditions). From these studies the Horizontal Gaze Nystagmus (HGN) test, the Walk & Turn, and the One Leg Stand were born.
Despite their fancy, scientific titles these studies have never been submitted for peer review or published in any scientific journals. Additionally, the 1977 study had a 47% false arrest error rate. Meaning 47% of the time the officer’s arrest was wrong. The 1981 study faired only slightly better, backing a 32% false arrest error rate.
Between 1995-1998 the National Highway and Traffic Safety Administration (NHTSA) conducted three sobriety test validation studies: the Colorado study, the Florida study, and the San Diego study. The point of these studies was to take the field sobriety tests out into the field under real conditions and have officers make arrest decisions. In the Florida study, 67% of all incorrect arrests failed the Horizontal Gaze Nystagmus test and 70% of subjects under 0.08 (i.e. not legally intoxicated) failed the walk and turn test. In the San Diego study, 52% of subjects under a 0.08 failed the walk and turn and 41% of subjects under 0.08 failed the one leg stand.
Finally in 2007 NHTSA conducted the Robustness study, specifically looking at the HGN test and determining the impact of test variations from protocol. While NHTSA believes this study validated the HGN test, looking at the numbers reveal the opposite. A false positive rate of 76.9% occurred when the stimulus speed was too fast (1 second instead of 2 seconds (protocol)). A false positive rate of 54.1% occurred when the stimulus height was either higher or lower than protocol (2 inches above eye level). A 69.2% false positive rate occurred when the stimulus was farther or closer away than protocol (12-15 inches in front of the face). The truth is the HGN test has an incredibly high false positive rate.
In conclusion, all three of the standardized tests are wrought with error. The tests are subjective opinions of an officer, often a predisposed officer, with little training or knowledge about the tests themselves. The best DWI attorneys in Austin, TX have the experience and tools to destroy the coordination exercises and win your DWI case.
