What is a DUI Field Sobriety Test?
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UPDATED: Mar 13, 2020
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Being pulled over by the police after a night on the town is never fun, and if a driver has been drinking it is especially bad news. He or she runs the risk of being subjected to field sobriety tests, and could even be arrested for a DUI.
What is a DUI?
A DUI, or driving under the influence, is illegal in all states. Any driver that has a blood alcohol content (BAC) of greater than .08 percent can be convicted of a DUI. In addition, even if the driver has a lower blood alcohol content, if he is showing signs of being impaired and unable to drive properly, he may still be arrested and convicted. Every state also subscribes to the No Tolerance law, which says people under the age of 21 can be arrested if they have a .02 percent or greater BAC. In some states, minors will be arrested if there is any alcohol at all found in their blood.
DUI Field Sobriety Tests
The DUI field sobriety test is actually a series of three different standardized tests given to drivers who have been suspected of driving under the influence of drugs or alcohol. The point of the tests is to verify the level of impairment, and establish probable cause to arrest the driver. Officers go through a formal training program to learn the tests, understand how to use them properly and interpret the results. According to the National Highway Traffic and Safety Administration (NHTSA), these tests are 65 to 80 percent reliable.
Standardized Field Sobriety Tests
The horizontal gaze test is the first of the standardized field sobriety tests. It works based on an involuntary jerking of a person’s eyeball, which will occur naturally as the person looks to the side. Normally this jerking only happens when a person rotates their eyes up high. When a person has ingested a substantial amount alcohol, this jerking is exaggerated and the eyes will have difficulty smoothly following a moving object. In this test, the officer will carefully watch a suspect’s eyes as the person follows a flashlight or pen that is being moved slowly back and forth horizontally. The officer has a list of several response indicators to check, and then based on how many criteria the subject displays, the officer will assess the probable level of alcohol in the driver’s blood.
The second and third tests are called divided attention testing, and consist of walking and turning, and then a one-legged stand. These types of tests are easily performed by most people who are sober, however, impaired persons have trouble with tasks that require them to do physical action while using their mind at the same time. When a person is impaired, he will typically sway, try to use his arms for balance or hop to stay balanced, and may have trouble listening to the instructions or will begin the test before the officer is finished giving the instructions. Again, the officer has specific behaviors he is looking for, and he will mark each indicator the subject shows and conclude the driver’s condition based on this data.
These tests can be effective in court testimony, but it is dependent on how many indicators of impairment were tracked by the officer while giving the tests. The greater the number of impairment indicators, the more convincing the tests are as evidence.
Other DUI tests
There are three other types of tests that are given to assess alcohol or drug levels. The first one is the breathalyzer test, and this is a portable machine that officers carry with them or use at the police station. It requires a suspect to blow into the machine to have her blood alcohol content measured. This test is fairly reliable, however, if a person has had a drink very recently the test is likely to register a higher score because of traces of alcohol that are still in the subject’s mouth.
A blood test is sometimes given to determine the level of alcohol or drugs in a suspect’s system. This is a more accurate test, but it needs to be performed at a police station. This test is often used after a suspect has failed a breathalyzer test.
Urine tests are sometimes given, however they are the least accurate and used only when the other types of testing cannot be done. These are also used to detect drugs in the system.
History of Field Sobriety Tests
Field sobriety testing has been used for decades, with various tests that require subjects to touch their nose with their eyes closed, or walk a straight line, for example. However, no studies had ever been done to determine the fairness or effectiveness of the tests that were being used. In 1977 and 1981, the NHTSA researched and developed a new battery of field sobriety tests, which are the ones in use today. Field sobriety tests are used only for the purpose of giving an officer probable cause to arrest a driver for suspicion of driving under the influence.
Problems with Field Sobriety Tests
One of the biggest problems with field sobriety tests is a failure of officers to rely on the standardized tests mentioned earlier. Instead, some officers use other unproven or anecdotal tests, which have not been standardized nor tested for reliability. For the standardized field sobriety tests, police officers undergo formal training to look for specific scoring factors, which then are evaluated to determine whether or not a subject is intoxicated. They can find a subject intoxicated only if a sufficient number of scoring factors have been identified. In addition, the standardized tests have been designed for and confirmed to detect a BAC of .08 or above. However, officers may claim that a subject has a higher level of intoxication such as .10 or .15 percent when they arrest him. This higher level of intoxication carries substantially larger penalties and fines, even though the field sobriety tests do not have the capability to confirm a BAC with that level of precision.