I am Joel Brand, and I defend DUI cases across California. If you were arrested for DUI on a night when it was raining, windy, or simply wet and cold outside, you may have a defense angle that many drivers never think to raise. This post explains how environmental conditions, especially weather, can affect the reliability of field sobriety tests, and why that matters when building your case.
Why Field Sobriety Tests Were Not Designed for Bad Weather
The three standardized field sobriety tests that officers typically use, the horizontal gaze nystagmus test, the walk-and-turn test, and the one-legged stand, were developed and validated under controlled laboratory conditions. Those conditions assumed a dry, flat, well-lit surface and a calm environment. Rain, wind, and cold temperatures are not part of the validation studies. When an officer administers these tests on a wet roadside shoulder in the dark while cars pass and raindrops hit you in the face, the test is no longer the same test.
How Rain Directly Affects Physical Balance
Wet pavement reduces traction under your shoes. A slight slope that would be easy to manage on dry ground becomes unpredictable when it is slick. Cold rain tightens muscles and slows your reaction time. Water in your eyes forces you to blink or squint, which can look like impairment on the horizontal gaze nystagmus test. All of these are physiological effects of weather, not of alcohol or drugs. If the officer noted that you stumbled on the walk-and-turn or put your foot down during the one-legged stand, the conditions that night may fully explain that result.
Wind and Its Effect on Divided-Attention Tests
Strong wind creates noise that makes it difficult to hear instructions clearly. If you misunderstood a direction because the wind was loud, that misunderstanding can look like confusion on the officer's report. Wind also physically pushes against your body during balance tests, which is a real mechanical force that even a sober person would have to compensate for. These are facts I look for immediately when I review an arrest that happened outdoors on a stormy or blustery night.
Uneven and Sloped Roadway Surfaces
Officers are supposed to find a level, dry surface before administering balance tests. In practice, the walk-and-turn and one-legged stand are often given on the side of a road, which almost always has a cross-slope to allow water to drain. That slope, even a slight one, creates a constant sideways pull on your balance. A wet, sloped shoulder on a rainy night is among the worst possible surfaces for a balance test. This is one of the common mistakes officers make at a DUI stop that a defense attorney can challenge.
What the Officer's Own Training Manual Says
The National Highway Traffic Safety Administration manual that governs standardized field sobriety testing specifically instructs officers to consider environmental conditions before and during the tests. An officer who proceeded despite rain, poor lighting, or a sloped surface without noting those conditions in the report, or who noted them and proceeded anyway, has created a potential issue for the prosecution. I look at the police report carefully for any mention of weather. Often it says nothing at all, which is itself a problem for the state.
The Police Report and Body Camera Footage
Understanding what is in the discovery packet after a DUI is one of the first things I work through with a new client. The police report will sometimes describe the road and lighting conditions. Body camera footage, if it exists and has not been lost, can show exactly what the surface looked like and whether rain was falling. Getting that footage quickly is important. I have written separately about officer mistakes at a DUI stop that show up in exactly this kind of review.
Can You Challenge the Field Sobriety Tests in Court?
Yes. A motion to challenge the weight or admissibility of field sobriety test results based on the conditions under which they were given is a legitimate defense strategy. The unfair field sobriety test defense is a recognized approach in California DUI cases. It does not automatically dismiss the case, but it can weaken the prosecution's evidence and change the way the judge or jury evaluates the officer's conclusions. In some situations it also supports a reduction of the charge, such as a wet reckless plea, if the physical evidence of impairment is thin.
What About the Breath or Blood Test?
Field sobriety tests are not the only evidence in a DUI case. The chemical test result matters too. Weather can affect how quickly alcohol absorbs into the bloodstream if you were cold and your body was under stress. The rising BAC defense may apply if your test was taken well after the stop. Cold and wet conditions can also influence breathing patterns, which may have an effect on breath test readings. This overlaps with the mouth alcohol defense in some cases involving residual breath patterns.
Medical Conditions That Weather Can Aggravate
If you have a pre-existing inner ear condition, a knee or ankle injury, or a neurological issue, cold and wet conditions can make those problems noticeably worse. Balance problems caused by a medical condition are not intoxication. California courts have recognized that medical conditions can be a defense to a DUI charge, and weather that aggravates an existing condition is part of that same argument.
What I Look for When Your Arrest Happened in Bad Weather
When a client comes to me after a wet-weather arrest, I request the full discovery packet, body camera footage, and dashcam video as soon as possible. I note the time of the arrest, the location, and the local weather records for that exact hour and place. Public weather data is admissible and can confirm rainfall, wind speed, and temperature. I also check whether the officer noted the conditions in the report and whether the test was stopped, modified, or simply administered on whatever surface was available. Every one of those details can matter at a hearing or at trial.
Does Refusing the Field Sobriety Tests Help?
In California, you have the right to refuse field sobriety tests without the same legal penalty that applies to refusing a chemical test. If you were not aware of that right and did the tests in the rain, it is not too late. The conditions under which the tests were given can still be challenged after the fact. This is general information and not a guarantee of any outcome, but the sooner you speak with an attorney, the better your chances of preserving the evidence that documents those conditions.
If you were arrested for DUI on a rainy or stormy night, I want to hear the details of your case. You can get a free written case analysis right here on this page. Call me directly at (888) 271-6644. I answer my own phone, 24/7. You can also read more from the DUI blog while you are here.