It has been the position of my office that field sobriety tests are often misinterpreted by police officers. Due to subjective nature of the tests, police officers often see clues that are either naturally occurring or unrelated to impairment.
The issue of the false positive is even more prevalent after an automobile accident because many of the effects of the crash can mimic impairment. For example, Horizontal Gaze Nystagmus (HGN) can occur naturally or after a person has received a head injury.
Many times, people do not even know they have received a concussion until days later; yet the police officer will think he sees HGN at the accident scene. To make matters worse, the police report may also state the suspect did not report any injuries, therefore, challenging the credibility of the defendant's later claim of injury.
Further, an accident can cause a person to lose motor skills and even slur speech; but police officers routinely ask individuals in shock to submit to physical agility testing such as the Walk-and-Turn test and the One-leg Stand. Those tests are difficult to do completely sober and on even ground, but officers have people submit to these tests after they have been involved in a collision. Of course, those tests have never bene validated by people who have been in a car accident or anything similar.
No one should ever place their future in the judgment of a police officer; especially after they have been in an accident.