WHERE THE PSUEDO SCIENCE BEGAN
Back in 1975 the National Highway Traffic Safety Administration (NHTSA) gave a grant to the Southern California Research Institute and namely a Dr. M. Burns. Dr. Burns took 6 of the then currently used Field Sobriety Test and tested which ones had any accuracy in determining if a person's blood alcohol level was .10 or greater.
The study yielded three field sobriety test. The Horizontal Gaze Nystagmus (HGN), Walk and Turn (WAT), and the One Leg Stand (OLS). These 3 FST's came to be known as "standardized" field sobriety tests, or SFST. The word "standardized" means that in order for the FST to be of any validity, the test MUST be given exactly the same each and every time. A good example of "standardized" is a McDonald's hamburger, whether you buy one in Los Angeles or Japan that hamburger is going to be exactly the same, or as we say, "standardized"
In the original study there were 238 participants who had a BAC range from .00 to .15 with some of the folks receiving a placebo drink. In the original study they started with 6 test that were evaluated in determining if a person was over the .10 legal limit. At the conclusion of the test the officer were only able to make a correct arrest 76% of the time.
What does that mean? that 24% of the time the COPS GOT IT WRONG!.