Drivers who are under investigation for DUI / DWI in Texas often take a field sobriety tests, such as the one-leg stand test, before being arrested. The one-leg stand test is one of three standardized field sobriety tests endorsed by the National Highway Traffic Safety Administration (NHTSA). Unfortunately, police don’t use the one-leg stand test to help them to determine whether a driver is impaired – the test is used solely to establish probable cause for an arrest and generate evidence for a court case. However, evidence such as the driver’s performance on the one-leg stand test can be effectively rebutted. An experienced Texas DUI / DWI criminal defense attorney will challenge the results of the one-leg stand test as part of an aggressive defense strategy.

The one-leg stand test is a divided-attention test, meaning that it’s meant to assess the mental and physical impairment caused by alcohol and/or drug use by requiring drivers to focus on two tasks at once. The prosecutor will try to use any variation between the way the test was explained and the manner in which the driver performed as evidence of intoxication.

Police administer the one-leg stand test by directing the driver to stand with his or her arms down and feet together during the instructions. The officer then tells the driver to raise one leg approximately six inches off the road with the foot parallel to the ground. The driver is instructed to look at his or her foot while counting “one thousand one, one thousand two …” until directed to stop. The one-leg stand test usually for 30 seconds.

As the test progresses, the officer will watch for four signs of impairment – using the arms to balance, swaying, hopping on one foot, and dropping the foot three or more time during the test. If police spot two or more of these signs, the officer will conclude that the driver has a blood alcohol content (BAC) of .10 percent or greater, and a drunk driving arrest will follow.

However, the one-leg stand test is hardly ironclad evidence. To understand why, it’s useful to learn how alcohol ingestion affects the human body. Experts in the field concur that alcohol intoxication causes both mental and physical impairment, but mental impairment always occurs first. Mental impairment caused by alcohol impairment cannot be masked. Therefore, if the driver doesn’t display any mental impairment, then any physical problems must be attributed to factors other than alcohol.

In order to convict a driver of DUI / DWI in Texas, the prosecutor must present evidence of both mental and physical impairment. The physical impairment displayed in the one-leg stand test can be attributed to sources other than alcohol, such as injury or illness. An experienced drunk driving defense lawyer will firmly establish that there are many factors unrelated to alcohol use that can explain why the driver might “fail” the one-leg stand test.

The one-leg stand test presents challenges for many drivers – plenty of people have trouble standing on one leg for 30 seconds without having even one drink. The one-leg stand test is especially difficult for people with inner-ear disorders or other balance problems, individuals with back or leg injuries, drivers who are over 65, and individuals who are overweight. Drivers who perform the test on uneven ground or who are wearing shoes with heels higher than two inches also face challenges.

Field sobriety test evidence is extremely subjective, and the tests’ inherent unreliability makes them susceptible to court challenges. Fort Bend drunk driving defense lawyer David Hunter's training as a certified field sobriety test instructor gives him the specialized knowledge needed to demonstrate that a driver’s poor performance in the one-leg stand test and other field sobriety exercises can be attributed to many factors other than alcohol intoxication.