One of the most damaging myths about a DUI stop is the idea that field sobriety tests are something you pass or fail, like a driving exam. I am Joel Brand, and I defend DUI cases across California. The reality is that these tests are not graded the way you imagine, they are not the objective measurements they appear to be, and for most people they were optional in the first place. Understanding how they actually work changes how you see your own arrest.
There is no score sheet you ever see
When an officer asks you to walk a line or follow a pen with your eyes, you probably picture a pass-fail result. There is no such thing. What the officer is doing is watching for specific clues, and counting them. The tests are scored by the same person who decided to pull you over and suspected you were drunk before the tests began. You never see the standard, you are not told what counts against you, and the officer's interpretation of what you did is the evidence.
The three standardized tests, and everything else
Only three field sobriety tests are considered standardized, meaning they were studied and given official scoring criteria. Those are the horizontal gaze nystagmus eye test, the walk-and-turn, and the one-leg stand. I break each of them down in the HGN eye test, the walk-and-turn, and the one-leg stand. Everything else an officer might ask, reciting the alphabet, counting backward, touching your finger to your nose, is non-standardized, with no validated scoring at all. Those are essentially the officer's personal judgment dressed up as a test.
They are designed to be hard, even sober
Here is what people do not realize. Standing on one leg for thirty seconds while counting out loud, or walking heel to toe in a perfectly straight line, are not things most sober people do well on demand, on the shoulder of a road, in the dark, in their street shoes, with headlights and a nervous officer watching. The tests were built to divide people, and the clues the officer looks for, a little sway, a raised arm, a missed heel-to-toe step, are exactly the things an anxious sober person produces. The deck is tilted by design.
Your body and the conditions matter
So many ordinary things skew these tests that have nothing to do with alcohol. Age, weight, injuries, inner-ear problems, fatigue, and medical conditions all affect balance and coordination. The surface you stood on, the slope, the weather, and even what you were wearing change the result. I have written specifically about how your shoes, clothing, and physical condition affect these tests, and about whether weather can affect field sobriety tests. None of that shows up in the officer's clipped summary.
For most adults, the tests were optional
This is the part that surprises people most. For an adult driver who is not on DUI probation, field sobriety tests are voluntary. You are allowed to decline them politely, and unlike refusing the post-arrest chemical test, declining the roadside coordination tests does not carry an automatic license penalty. They exist to help the officer build probable cause against you, which is why I explain when and how you can refuse field sobriety tests. People perform them because they assume they have no choice, and that assumption hands the officer evidence.
How I attack them later
Even when the tests were done, they are far from the end of the story. Bodycam footage often shows a person doing better than the report claims. The instructions are frequently rushed or unclear, the conditions are rarely ideal, and the officer's clue-counting is open to cross-examination. I describe this approach in the unfair field sobriety test defense. A jury that watches the actual video often sees something very different from what the words on the report suggested.
The eye test is the strangest one of all
The horizontal gaze nystagmus test deserves special mention because it is the one people understand least and trust most. The officer moves a pen or finger and watches your eyes for an involuntary jerking motion, and then tells you that jerking proves intoxication. The trouble is that you cannot see your own eyes, you have no idea what the officer claims to have observed, and nystagmus has many causes that have nothing to do with alcohol, including fatigue, certain medications, and natural variation between people. It is the least transparent test of the three, which is exactly why I scrutinize how it was administered.
What the report leaves out
A police report describing your field sobriety tests is a summary written by the person trying to justify your arrest. It records the clues that hurt you and rarely the moments that helped you. It does not capture how rushed the instructions were, how uneven the ground was, how cold or frightened you were, or how reasonable your performance actually looked to a neutral eye. That gap between the written narrative and the real video is where many of these cases turn, and it is the first place I go when I get the footage.
What you should take from this
None of this means field sobriety tests are meaningless to your case. They carry real weight with a jury if they go unchallenged, which is precisely why they should never go unchallenged. The mistake is treating them as a verdict you already failed. They are evidence, and like all evidence they can be questioned, contextualized, and in many cases substantially undercut.
The bottom line
Field sobriety tests are not a pass-fail exam. They are subjective, condition-sensitive observations, scored by the officer who already suspected you, and for most adults they were never mandatory. If your case rests heavily on how you supposedly did on the roadside, that is a case with real room to fight. Get a free written case analysis below, or call me directly at (888) 271-6644. I answer my own phone, 24/7. You can also read more from the DUI blog.