The most common tools a police officer will use to determine whether a person is intoxicated during a DUI stop are the standardized field sobriety tests. According to VeryWellMind, the National Highway Traffic Safety Administration developed these tests in the 1970s. The first test is the nystagmus test. A subject may also have to take a nine-step walk test. Others may have to undertake the one-legged stand. 

The horizontal gaze nystagmus is a test where you gaze at an object, usually a pen with your eyes while the officer checks your eyes for certain indications of intoxication. There are a total of six clues that the officer is looking for, three in each eye. Exhibiting four of those clues is an indication that the subject is intoxicated. The nine step walk and turn involve walking a straight line, touching heel to toe for nine steps, taking a small series of turns and then taking an additional nine steps back to your starting point. 

According to FindLaw, there are eight clues that the officer is looking for during this test, and showing two of those clues is an indication of intoxication. The one-leg standing test involve standing on one leg for a period of 30 seconds. There are four clues that the officer looks for during that test, and exhibiting two of them is an of intoxication. 

Failing the standardized feels right test is not itself absolute proof of intoxication. The tests themselves are subjective, which means that they are not foolproof. Additionally, these tests are not performed exactly the way that they are supposed to be. You can argue with the test results themselves were invalid and might be capable of keeping them at trial. Far too many people give up if they’re arrested for a DUI charge before speaking with an experienced attorney.