The vast majority of DWI arrests involve Standard Field Sobriety Test (SFST). The 3 tests are the Hortizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand. These tests were developed by the federal government to help arrest drivers for DWI. SFSTs and the “science” behind them have never been published in any peer reviewed journal. Still, they are a standard for DWI enforcement and almost always admitted in every DWI trial.
Steve Rubenzer is a board certified forensic pyscologist and an expert on SFST. His paper, the The Psychometrics and Science of the Standardized Field Sobriety Tests is a must read for any DWI defense lawyer.
I emailed some questions which Dr. Rubenzer was kind enough to answer.
1. What should the public know about field sobriety testing?
Depends on their situation. If stopped by the police, they usually are under no obligation to perform them. If on a jury, realize that there are many problems with them.
2. How accurate are SFSTs?
That’s not easy to answer, because it depends a great deal on things like what subjects are used (high school gymnasts vs. middle aged and old fat people), BAC distribution, and ratio of sober to intoxicated subjects. Overall accuracy rates are not useful, which is why most researchers don’t rely on them.
3. What could be done to improve SFST? Better training and monitoring of police administration.
More research. Possibly expanded scoring (from present/absent to Present/absent/?) Probably should add some physical tests that don’t depend on balance and some mental tests, as WAT and OLS are largely redundant.
4. Would you take SFSTs?
Depends if I thought I would pass them
5. If SFST’s are flawed, why are they so prevalent?
There is a real need for something that does what the SFSTs are supposed to do.
6. Do you believe that innocent driver’s are convicted via SFSTs?
Almost certainly given the large number of DWI stops. No test is perfect, and even if the false positive rate is say 5%, 5% of one million is 50,000.