Criminal Defense in Orange County

Are All Field Sobriety Tests Reliable?

It is well-known that drinking alcohol can cause mental and physical impairment that may affect a person's ability to safely operate a motor vehicle. However, it is still controversial whether a non-chemical field sobriety test can adequately determine whether a particular individual was driving under the influence at a particular time. Non-chemical field sobriety tests include things like asking the driver to put his finger to his nose, counting backwards from 100, and walking in a straight line. Non-chemical sobriety tests have fundamental flaws that make them unreliable.

There is little scientific data to support the reliability of these tests, and for the studies that do exist, questions have arisen about the design of the studies. These studies have resulted in variations between different drivers who were subject to the same amount of alcohol impairment. There have also been inconsistent results by the same driver under similar conditions. The tests may also be unreliable without a baseline determination of the driver's performance level when they were sober. The driver might also have medical or other conditions that may affect their performance.

Furthermore, unreliability may result when officers in the field are not adequately trained to properly administer and evaluate the tests. Despite their unreliability, field sobriety tests are still used by police officers to accomplish several ancillary goals, such as enabling them to establish probable cause for a stop or an arrest, assisting them in proving possible physical or mental impairment near the time you were observed driving, or establishing the causal relationship between your driving behavior and alcohol. Contact our firm to find out how you can fight faulty DUI evidence.

What is the most reliable way to determine intoxication?

Determining a person's level of intoxication is a tricky question, and methods of evaluating it are generally divided into field sobriety tests and chemical tests. It is generally agreed that the best indicator of driver impairment is a simple blood alcohol test. Chemical tests are able to measure a person's blood alcohol concentration objectively (within a certain margin of error depending on the machine), which makes the question of impairment a fairly straightforward and scientific one.

Field sobriety tests, on the other hand, are less reliable, even if you are sober. This is because they are inherently subjective and not administered the same way by all officers or performed the same way by all people. If you were arrested for driving under the influence on the basis of a field sobriety test, an Orange County DUI lawyer may look to see if there are weaknesses in the tests that were performed and whether there are other possible explanations for your performance.

Not all field sobriety tests are reliable, despite what the prosecution would have you believe. In fact, a study that was conducted by the National Highway Traffic Safety Administration concluded that, of the tests administered most commonly by police officers, only three could accurately determine a driver's level of impairment. Furthermore, these three tests (the horizontal gaze nystagmus, the walk and turn, and the one leg stand test) are only reliable when used together and properly administered.

Factors That Could Affect the Results of a Field Sobriety Test

There is little scientific evidence to prove that field sobriety tests are reliable at all. Many have not been researched, and a few have yet to be validated as reliable measures of a driver's alcohol impairment. Many of these tests merely gauge a driver's ability to divide their attention. These tests can have their results affected by the driver's medical condition or by environmental factors, such as the slope of the road on which the tests were administered. Yet, despite lacking the scientific evidence to support their use, these tests are still used by law enforcement to justify DUI arrests.

Researchers commissioned by the National Highway Traffic Safety Administration and the United States Department of Transportation claim that these tests do not indicate actual driver impairment. These researchers have expressly stated that "driving a motor vehicle is a very complex activity that involves a wide variety of tasks and operator capabilities. It is unlikely that complex human performance, such as that required to safely drive an automobile, can be measured at roadside."

Some police departments agree with this assessment, especially with respect to the nystagmus test. Nystagmus is an involuntary jerking or bouncing of the eyeball that occurs when the inner ear system or the oculomotor system is disturbed. Horizontal gaze nystagmus (HGN) may be caused by alcohol impairment, due to the fact that alcohol limits the brain's control of the eye muscles. However, since there a many other causes, The California Highway Patrol Manual states that signs of HGN are not supposed to be considered signs of driving impairment or driving under the influence.

If you have been charged with DUI in Orange County and the arresting officer used a field sobriety test during their investigation, you should not hesitate to call our firm today for a free consultation.