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How Accurate Are Field Sobriety Tests?

In order for law enforcement to legally arrest someone, charge them with DUI, and then have them take a chemical BAC test, officers must first legally establish probable cause. Probable cause is a “reasonable suspicion” that someone has committed a crime based on available circumstantial evidence. In order to establish this standard, officers use field sobriety tests, which are tasks that are designed to emphasize signs of intoxication and thus establish probable cause.

In theory, field sobriety tests are impossible for someone who is legally intoxicated to pass, while those who aren’t intoxicated can pass them quite easily. Thus, officers then make an accurate arrest based on the results. So reasonably, this means most people would expect and think that field sobriety tests have been refined and standardized to ensure accuracy.

However, these theories don’t work out all that often in real-world circumstances, and the truth about these tests shocks a lot of people: despite years of refinement and testing, they’re still woefully inaccurate and lead to all sorts of wrongful arrests and accusations. These tests are difficult—even for sober people in a lot of cases, because they force your brain to try and comprehend different types of tasks that you wouldn’t otherwise have to do normally.

Accuracy Studies

Dr. Spurgeon Cole of Clemson University performed a study in which he showed trained police officers video of people taking approved field sobriety tests that were conducted properly. He then asked the officers to identify how many people they believed were actually intoxicated. Officers on average found that a little under half of the people were intoxicated. Only there was one problem: the truth is none of the people in the videos were intoxicated. They were all completely sober, and yet officers still failed and found them to be inebriated nearly half of the time. At that point you’re almost better off flipping a coin than you would be trusting an officer’s judgement!

The prevailing theory for this is that officers tend to wildly overestimate someone’s intoxication level. Human nature is prone to bias, and in many cases officers are biased toward finding someone who is drunk, arresting them, and getting them off the road. Unfortunately, this leads to a lot of people being falsely arrested and forced to take a chemical test when they aren’t even over the legal BAC limit, and thus no crime has ever occurred!

When field sobriety tests were first standardized after a thorough study back in the 1970s, the Southern California Research Institute admitted that the tests they used were hardly accurate and were wrong nearly half of the time. By the 1980s, they had obtained some better data—a success rate of around 70 percent. Today, that number is up as high as 91 percent, but the truth of the matter is even this is misleading. Some deeper dives into these numbers have shown that in getting the 91 percent number, subjects in these tests included people who were so far over the limit that the results of their field sobriety test didn’t matter: anyone could have known they were drunk. Likewise, when officers were asked to estimate a subject’s BAC for this test, they were allowed to take breathalyzer results into consideration. In other words, they were asked to take a test and then given an answer sheet to complete it!

What This Means for You

So what does that mean for you? As a citizen, if you’re questioned by an officer and they ask you to take a field sobriety test, you are allowed to decline. Since you have not been placed under arrest, you are not required to submit to a chemical test, and officers are not allowed to require you to submit to a sobriety test. Officers may still choose to arrest you, but the truth is that if they arrest you and you are not above the limit, they could get in big trouble in a hurry for falsely arresting you.

If you’ve been arrested and charged with driving under the influence, speak with a Scranton DUI lawyer at the Law Offices of William D. Thompson by calling (570) 666-1068 today!
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