In Wisconsin, by statute, probable cause to arrest for drunk driving is required before a police officer can ask a driver to submit to a preliminary breath test. Probable cause to arrest for drunk driving is also required, both by statute and the Constitution, before a police officer can ask a driver to submit to a blood test. Often, police rely on phony evidence to justify an stop. Another Madison cop testified, under oath, that he believed the fact that a driver heading to the suburbs in evening rush hour traffic had his tie loosened from his shirt collar was a sign of intoxication. These officers are, of course, still on the streets.
Police also rely on bogus evidence.
No one could do it, even sober. So, the feds rejected it as a standardized test. Standing on one leg is the natural activity of the flamingo, not the human being. Police claim these tasks determine intoxication by establishing that a driver has poor balance. But putting a person into a stance that is inherently imbalanced doesn't measure balance.