Answer: Not always. It’s hard for anyone to say an exact percentage of how accurate they are. NHTSA says that they’re 80% accurate based off the fact that the HGN is considered accurate 77% of the time, the walk-and-turn is at 68% of the time and the one-leg-stand is 65%. These are based on a .10 and above breath alcohol content. However, there’s been other studies that have showed the decision to arrest and all those lab tests that were conducted in Florida, California, Colorado, that they had high numbers of 37% to 40% of the time the officers were wrong. And they even had cases where people were absolutely sober. So they placed it at a .10 and above and then lowered it down to .08 level of alcohol so that way if you’re that or above, they should be able to tell on the test.
However, this all comes back to whether the officer is properly trained, the person administering the situation. If you have someone going uphill at a slant on a walk-and-turn, it would be hard for anybody. Plus, there’s factors that play in. The age of a person. NHTSA and the studies show that people 65 years of age or older may have trouble doing the test. If they have back problems, inner ear, middle ear problems, had recent head injury.
All these things are factors. If you’re more than 50 pounds overweight, you’ll have issues with the walk-and-turn and the one-leg stand. Which brings it back to only having HGN to go off of, and you can’t go off of just one test. That’s why they’re considered a battery of test because, like I said earlier, the first test, the HGN, there’s over 300 things that can affect HGN. So it’s closer to 70% accurate.
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