I'm going to say this up front. This is kind of technical. It is actually posted as much for other attorneys and judges (yes, they read this site!) as for the layperson.
But I think you'll understand it, too. It turns out that the most "scientific" of the Field Sobriety Tests is a complete FRAUD.
We discovered something very interesting when the federal government finally revealed the raw data from their evaluation of field sobriety tests. We discovered that--from the government's own data--the tests don't work. Even when they are conducted by experts on physically fit subjects in a laboratory in perfect conditions, the HGN test will show that up to 77% of sober drivers are over .08.
Many people are familiar with the so-called "eye test" (sometimes called the "pen test") given by the police when they pull over a suspected drunk driver. Technically, it's called the "Horizontal Gaze Nystagmus" test, or HGN. Supposedly, the police are looking for jerkiness in your eyeballs which shows that your blood alcohol limit is above the legal limit. In Florida, the HGN is considered the most scientific of all of the field tests. But it turns out that the HGN test is bunk!
Here's a short video that shows something shocking. When the U.S. Department of Transportation tested the Horizontal Gaze Nystagmus test in a laboratory, it didn't work. Right. It didn't work. In fact, the government's own research showed that 67% of people with blood alcohol under .08 wind up being arrested if the police rely on the HGN test. It is a grave mistake to subject yourself to the test on the streets if you've had so much as a sip of alcohol. Even if you are well under the legal limit, there is a 2 out of 3 chance that you will be arrested if you take the HGN test.
Not only that, but the government tried to hide the fact that the test doesn't work. When they published their results, they changed the definition of how many "clues" constituted a positive finding. And they also moved the bar from .08 to .06 for a false positive. Both of those changes made it look like the test was reliable when it's not.
Again, the video is complicated and it moves pretty fast. But if you stop it and look at the tables and illustrations, I think you will see that there is no science, and only fraud, behind the Horizontal Gaze Nystagmus test.