How reliable are field sobriety tests?

On Behalf of | Nov 5, 2019 | Criminal Defense |

Drunk driving has been a significant issue in the United States for multiple decades. As a result, police officers have taken numerous steps to ensure that the road is free from intoxicated drivers. One measure that has not changed much, however, is the field sobriety test.

Field sobriety tests have been used by officers for many years and aim to determine whether a given driver has been driving under the influence. These tests measure cognitive ability and driver fitness based on the performance of basic tasks. If the driver is unable to perform these tests successfully, the officer will have probable cause to make an arrest.

Since the results of a field sobriety test assist in determining probable cause, it is easy to assume that these examinations are always accurate. Field sobriety tests have indeed proven to be an effective tool for officers, but they are not without flaws.

Statistical review

Scientists have challenged the reliability of field sobriety testing for many years. This is because even the most consistent examinations still occasionally prove to be inaccurate. During the 1970s, the Southern California Research Institute recommended that officers use the horizontal gaze nystagmus, walk and turn and one-leg stand tests because they were the most consistent.

However, even when used in conjunction, these three tests still yielded accurate results only 82% of the time. Individually, the horizontal gaze nystagmus was proven to be the most accurate at 77%, followed by the walk and turn at 68% and the one-leg stand at 65%.

Common issues

There are a variety of different reasons why field sobriety testing is not always accurate. Nervousness and anxiety can cause people to function in a way that may closely resemble intoxication. Some people are also naturally clumsy and uncoordinated, which can make even the most basic tasks look sloppy.

Field sobriety testing also does not account for health issues, handicaps and advanced age. Naturally, as a person grows older, performing rudimentary tasks becomes more difficult. The same can be said for someone who has endured a significant injury. They may have issues with balance or coordination, which can have a direct impact on their ability to complete an examination.

It is also possible that the police could make an error while administering the test. The officer may not have much experience or lack an understanding of how a given subject would perform differently based on the amount of alcohol he or she consumed.

Field sobriety tests can undoubtedly be useful under the right circumstances. They can provide evidence that keeps reckless drivers off the road and ensure your safety. However, they do have the potential to be unreliable and are therefore an imperfect science in determining whether someone is intoxicated.