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Moncks Corner Legal Issues Blog

How accurate are Field Sobriety Tests?

Members of law enforcement typically demand that a driver who is suspected of driving under the influence perform a battery of roadside tests to begin building a DUI case. Field sobriety tests do not measure alcohol concentration, but police regularly rely on the results of these tests to gauge potential impairment. These tests are generally accepted in court to show that the office had probable cause to make a DUI arrest. While they are generally approved, they are not without their flaws.

Many people complain that many of the tests are not only too subjective, but are designed for the driver to fail. False positives are common, especially in bad weather, or due to nervous reactions of drivers who have been pulled over. Commentators have long objected to the use of these tests, stating that few people have the physical agility or athletic coordination to pass the one-legged stand, or the walk-and-turn when sober, let alone after a night out. Of course, police counter that officers are trained to understand when nerves, or inability, are the root cause of a failed FST.

Is a 50 percent or 75 percent accuracy rate acceptable ao support an arrest?

There may be some irony in the thought that some commentators say that the one-legged stand is the least subjective FST. The irony is highlighted by the fact that research shows that the one-legged stand is the most flawed test recognized by the National Highway Traffic Safety Administration is the one-leg stand. Researchers found that in a clinical, laboratory setting with ideal conditions, roughly 47 percent of those tested failed the test when not over the legal limit to drive. Overall, more than a quarter of the study participants would have been falsely arrested for drunk driving.

Unfortunately, probable cause for arrest does not require proof beyond a doubt. But, there may be cases where the evidence is not sufficient to support the lower probable cause standard.

Challenging DUI charges has many steps, and requires a great deal of legal analysis. While challenging FSTs is only one concept – which may not be appropriate in every case — it is critical to work with a skilled criminal defense lawyer. Every aspect of a DUI case should be handled with integrity to maintain credibility in the drive toward reaching the best possible outcome.