The Standardized Field Sobriety Tests are Accurate Enough at Detecting BACs Above .08 According to the NHTSA.
You see them in movies all the time, and perhaps you’ve even seen one—or experienced one—in real life. Field sobriety tests are used to give officers probable cause to arrest you for drunk driving. They use them all the time, but how accurate are they? Do they really give the officer a clear indicator of your ability to drive a vehicle, and should they be trusted as indisputable truth?
While they can be used to give the officer probable cause to arrest you if you fail, many researchers will say that they’re not entirely accurate. And there are studies to back this finding up, too. In the 1970s, there were dozens of different field sobriety tests in use by police everywhere. No two were the same, and there was no conclusive evidence that any of them were accurate.
The National Highway Traffic Safety Administration asked the Southern California Research Institute to evaluate these tests and figure out which were the most accurate to streamline the process.
Ten officers watched several subjects perform a variety of tests and then were asked to identify which participants had a blood alcohol concentration of .10% or more. Based on the accuracy with which they identified the high BAC in each participant, they choose three field sobriety tests as the most accurate. The winners were the Horizontal Gaze Nystagmus, the One-leg Stand, and the Walk-and-Turn.
The Horizontal Gaze Nystagmus requires you to follow with your eyes an object (pen or light) that the officer is holding and moving from side to side.
The One-leg stand requires that you hold one foot six inches off the ground and count from 0 to 30 without putting your foot down.
The Walk-and-Turn test requires that you walk in a straight line for nine steps, touching your heel to your toe with each step, then turning around and walking the nine steps back to the starting point in the same way.
In the preliminary tests at the Southern California Research Institute, the officer error rate was 47% in predicting the BAC of a person based on the field sobriety test results. So, unfortunately, it didn’t seem that these tests were very accurate, despite the fact that they were the most reliable of all the options.
Since the original assessment, these three field sobriety tests have been standardized. The one-leg stand has a 65% accuracy rate, the walk and turn has a 68% accuracy rate, and the horizontal gaze nystagmus has a 77% accuracy rate. When used together, they have a combined score of 82% accuracy.
That’s not the worst, but it’s also not great. The higher success rate is also contingent on the officer using all three instead of just one or two, which means you’re at the mercy of the officer’s discretion if you are asked to perform a field sobriety test.
Because there’s no scientific basis for the reliability or accuracy of these tests, expert witness accounts and experienced defense attorneys can help you challenge your DUI conviction based on the results of these tests.
Call the Johnson Law Firm to speak with an Experienced DUI Attorney
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