The Horizontal Gaze Nystagmus (HGN) test is often the first one used to assess a person's level of intoxication. Horizontal gaze nystagmus is the term used to describe the involuntary jerking of a person's eye which can occur when one's gaze is cast to the side. Nystagmus is used as an indicator of impairment because it becomes exaggerated when intoxicated and can occur at lesser angles than those that would normally provoke an eye jerk. Typically, an officer will move a flashlight or lighted pen and ask the suspect to follow the light with their eyes. This allows the officer to track the eye movement of the suspect and identify whether or not they are able to accurately follow a slowly moving object without any eye jerking or deviation. When an individual is unable to complete the light tracking without faulty eye movement, officers may have further reason to assume that the suspect has been driving under the influence. While NHTSA research has found that about 88% of persons who show signs of horizontal gaze nystagmus are also intoxicated, it cannot be assumed that this is the only cause. The failure in this test lies in the fact that nystagmus is a common clinical condition that plagues several thousand people throughout the U.S. Furthermore, it often goes unrecognized and undiagnosed. Therefore, it could be argued that the field sobriety test involving HGN is not a great way to identify intoxication, as the results of the test could simply signify that the person suffers from a nystagmus condition.
The second standardized test used by police officers during a roadside check for sobriety is the Walk and Turn test. This is a type of "divided attention" test which requires a driver to utilize both listening/ comprehension skills as well as physical capabilities; the theory being that impaired persons are unable to divide their skills between mental and physical tasks. When a suspect is directed to perform the Walk and Turn test they will be asked to take heel-to-toe steps along a straight, linear path. After a certain amount of steps have been taken in one direction, the individual will then be asked to turn around on one foot and repeat the heel-to-walking in the other direction. Among the indicators that officers will be looking for during this type of test are a suspect's ability to keep balance, turn properly, take the correct number of steps in the correct way (i.e. heel to toe), stay on the linear path, walk the line without using arms to balance, and listen to and follow instructions properly. However, it can be more than difficult for even unimpaired individuals to successfully follow some of these procedures. Therefore, relying on the indication of two more of these signs for confirmation that a person's cognitive and mental skills are impaired is an unsafe way to determine impairment.
The third of the standardized tests is the One Leg Stand test. Like the Walk and Turn test, this is one that focuses on the ability of person to utilize their divided attention skills. Upon being pulled over, an officer may ask the driver to stand with one foot on the ground while the other is held approximately six inches off the ground. At the same time, suspects will be asked to count by thousands while the officer conducting the test records signs of impairment for a period of 30 seconds. During this timed event, law enforcement officials will be looking for indicators such as swaying, unsecure balance, hopping to maintain stance, using arms to help with balance, and putting your raised foot down. According to NHTSA, a little over 80% of persons who exhibit two or more of these behaviors during their performance of the One Leg Stand will have a blood alcohol concentration level above the legal limit. Again, what is failed to be mentioned is the fact that this can be a less than easy task for anyone, sober or not. Some people naturally have a more difficult time maintaining their balance in even the most normal of circumstances, making an on-the-spot test of balance one that could yield inaccurate results.
The inadequacy of these standardized tests has not failed to be recognized. In fact, other non-standard tests have been put in place to supplement those implemented by the National Highway Traffic and Safety Administration. The Rhomberg Stationary Balance Test requires drivers to stand with feet together while leaning back to look up at the sky and holding their arms out to the side. The Finger-to-Nose Test asks suspects to close their eyes and then touch their nose with their pointer finger. These, along with standardized test methods, are believed to be the clearest ways to quickly identify alcohol or drug impairment. Unfortunately, they are also tasks which many non-intoxicated individuals would be unable to complete if asked to do so. Therefore, their accuracy is less than reliable and should not be used as a primary source of intoxication identification. If you have recently been arrested based on your performance of a field sobriety test such as those described above, then you should most definitely challenge the charges that have been brought against you. With the help of a DUI defense attorney you can use the inaccuracies of these methods to prove that your DUI arrest was not founded on sound evidence and should not lead to a conviction.