The Standardized Field Sobriety Test is composed of three different tests that can be administered separately or collectively. The National Highway Traffic Safety Administration (NHTSA) sponsored the research of these tests and the findings are based upon the work of the Southern California Research Institute. The One-Leg Stand test involved an individual standing on one leg and remaining balanced for 30 seconds. The officer is looking for signs such as swaying, hoping to stay balanced, using arms to remain steady and having to put down a foot. The research has stated that 83 percent of the people that show two or more of the signs officers are looking for will have a Blood Alcohol Content (BAC) of .08 or higher.
For the Walk and turn test, officers will ask the individual to walk a line with one foot in front of the other, then pivot and return back in the same manner. During this test they will look for eight signs that may be indicators of impairment. Allegedly 79 percent of people that show two or more of the signs will have a BAC level of .08 or more. During the Horizontal Gaze Nystagmus test, an officer will be assessing the eyes and looking for three indicators in both eyes. An object will be used, such as a flashlight and the individual will be asked to follow it with their eyes. The officer will look for if the eyes can move smoothly, if jerking of the eye becomes evident when it is at maximum deviation and if the jerking of the eye begins within a 45 degree angle from the center. The NHTSA states that based off of their research, 88 percent of individuals can be classified as having a BAC of .08 or above if they exhibit four or more signs between their two eyes.
While the research states that the tests can be useful in determining which individuals have a higher level of alcohol in their system, they are not 100 percent. There are a number of factors that can cause a person to appear guilty when they are not. One of these is if the officer is not thoroughly trained in administering the tests and as a result of inadequate competency the results can be skewed. The burden of proof is put on the accuser in DWI cases and they will need to show convincing evidence that you were driving while intoxicated. Field Sobriety Tests are a way that many officers seek to prove this. Charges of drinking and driving can still be fought even after taking a Field Sobriety Test and it is best to do this with the representation of an adept attorney.