Illinois police officers have multiple tools at their disposal for determining whether a driver might be intoxicated. Most people are aware of Breathalyzers and blood tests, which are used to determine blood-alcohol content, but few understand that there is also a third option. Drivers pulled over on the suspicion of drunk driving might be asked to perform field sobriety tests.
The National Highway Traffic and Safety Administration endorses the Standardized Field Sobriety Tests -- SFST -- which police officers generally use to assess a driver's physical ability, balance and attention level. There are three separate components to the SFST, and attending officers usually carry out all three so that their results may be viewed as a whole. Breathalyzer or blood tests still usually follow any roadside field tests.
The horizontal gaze nystagmus test is used when observing involuntary eye jerks, which naturally occur as people move their gaze from side to side. However, this natural movement becomes exaggerated when someone is under the influence of alcohol. This makes it difficult for individuals to smoothly follow any moving object.
For determining a driver's ability to complete tasks while experiencing divided attention, officers use the walk and turn. This requires an individual to walk a certain distance in a heel-to-toe fashion, maintain a straight line, then turn on one foot and repeat the process. It is a relatively straightforward task.
The final piece of the SFST is the one-leg stand. Drivers must lift one of their feet approximately six inches, then count out 30 seconds. They must demonstrate that they can maintain balance without swaying, using their arms or hopping around.
The results of these tests are often used as evidence when bringing drunk driving charges against Illinois individuals. However, they are usually used in addition to a BAC test and not as a replacement. Since drunk driving cases tend to move much quicker than other criminal allegations, it is usually a good idea to review field sobriety tests, BAC results and other related evidence as soon as possible, as doing so may help defendants build a strong foundation for their defense.
Source: FindLaw, "Field Sobriety Tests", Accessed on Nov. 9, 2017