The story of the trooper who arrested eight sober drivers seems less surprising when you examine the government’s own research on these tests. The data, collected over decades, shows wildly different accuracy rates depending on the study, highlighting just how subjective these tests can be.
Let’s look at the original laboratory data from the National Highway Traffic Safety Administration (NHTSA) for each test’s ability to determine impairment:
Horizontal Gaze Nystagmus (HGN): The eye test was found to be 77% accurate.
Walk-and-Turn (WAT): The line-walking test was found to be 68% accurate.
One-Leg Stand (OLS): The balance test was found to be only 65% accurate.
Think about that: the original research showed that two of the three core tests were wrong about a third of the time.
The simple fact is none of these tests are 100% accurate. For the person on the side of the road, that percentage gap isn’t just a statistic; it’s the potential for a life-altering, wrongful arrest. When an officer with a history of getting it wrong is administering these flawed tests, it’s a recipe for injustice.
