DWI Misconception: I Think I passed (did well) on the Police Field Sobriety Tests

The walk and turn has over a hundred little steps, so even a 97% correct is a big fail. Police criteria on whether you pass or fail field sobriety is extremely subjective. What exactly is involved in the walk and turn test?
Can we defend this test just based on common sense? Read on to see how we attack the fundamentals of this rather easy test.