An officer says you "failed" the field sobriety tests. What that means is that the officer, standing on a roadside at night, counted a certain number of "clues" while watching you — and decided you had enough. Brian Foley, who trained on the tests as a prosecutor, explains in this video why that decision is far less scientific than it sounds.
What the tests are
NHTSA's three standardized tests are the horizontal gaze nystagmus (HGN) eye test, the walk-and-turn, and the one-leg stand. Each is scored by the number of "clues" the officer observes: stepping off the line, using arms for balance, starting too soon, missing heel-to-toe. Two clues on the walk-and-turn, or two on the one-leg stand, is a "fail."
Why they are subjective
- The officer decides what counts. Was that a "step off the line" or a wobble? Did the arms come out more than six inches? There is no measurement — only an opinion, formed by someone who has already decided to investigate you for DWI.
- Conditions matter and are usually ignored. NHTSA's manual says the tests should be given on a dry, level, hard surface with adequate lighting. Roadside shoulders at 2 a.m. rarely qualify. Wind, rain, passing traffic, and strobing emergency lights all affect balance.
- The person matters. Age over 65, being more than 50 pounds overweight, back, leg, or inner-ear problems, and footwear with heels over two inches all invalidate the balance tests under NHTSA's own guidance. Officers rarely ask.
- The instructions matter. The tests are only "standardized" if administered exactly as trained. A skipped instruction, a demonstration done wrong, or a rushed explanation means the result is unreliable — and cross-examination of the officer against the manual shows it.
- Even done perfectly, they are wrong often. NHTSA's own validation studies put the error rate for sober subjects well above zero. A sober, nervous person on a roadside can fail.
What the defense does with this
The in-car and body-camera video is compared, clue by clue, against the NHTSA manual. Every deviation — in conditions, in administration, in scoring — is a reason the "failure" is not evidence of intoxication. In many Galveston County cases, the FSTs are the State's only evidence of impairment beyond the officer's opinion. Undermine them and the case follows.
Read more on our field sobriety tests page, or call or text (409) 877-4909 for a free consultation with our Galveston DWI attorneys.