Disputing Field Sobriety Tests: Factors That Can Invalidate Their Accuracy

If you are driving down Orange Street in Redlands or cruising near the San Bernardino Justice Center and see those red and blue lights, your heart probably skips a beat. When a police officer asks you to step out of the car to perform physical exercises, they are not looking to see if you are a good athlete. They are building a case against you. Most people assume that if they “fail” these roadside gymnastics, they are guilty. We are here to tell you that these tests are deeply flawed. Understanding the science and the law behind disputing field sobriety tests is the first step toward exposing factors that can invalidate their accuracy.

At Patrick Silva, Attorneys at Law, we do not accept an officer’s word at face value. We know that police in San Bernardino County frequently mess up these tests. We have spent years studying the National Highway Traffic Safety Administration (NHTSA) guidelines. We have even completed the same 24-hour intensive training that officers undergo to learn how to administer these tests. The difference is, we actually learned the material. We know how to cross-examine an officer until they admit they gave the test wrong.

The Three Standardized Tests and Their Flaws

The NHTSA has established three specific exercises known as Standardized Field Sobriety Tests (SFSTs). These are the only tests backed by significant research, but they are still prone to massive error. If an officer asks you to touch your nose or say the alphabet backward, they are using non-standardized tests that have almost no scientific validity in a California courtroom.

Horizontal Gaze Nystagmus (HGN)

The HGN test involves the officer moving a pen or stimulus in front of your eyes. They are looking for an involuntary jerking of the eyeball. According to the NHTSA DWI Detection and SFST Instructor Guide, there are three specific clues they look for in each eye. But there are over 40 types of nystagmus that have nothing to do with alcohol. Conditions like inner ear infections, certain medications, or even eye strain can cause your eyes to jerk.

Walk and Turn (WAT)

This test requires you to take nine heel-to-toe steps along a straight line, turn in a specific way, and walk back. The officer is looking for eight specific clues, such as losing balance or taking the wrong number of steps. In reality, many sober people cannot do this perfectly under the stress of a police encounter on the side of a busy San Bernardino highway.

One Leg Stand (OLS)

You must stand on one foot while counting aloud for about 30 seconds. The officer looks for four clues: swaying, using arms for balance, hopping, or putting your foot down. This test is essentially a balance check. If you are over 65 years old or more than 50 pounds overweight, the NHTSA admits this test may not be accurate.

Physical and Medical Factors That Ruin Test Results

Police officers often treat everyone like they have the body of a 20-year-old Olympic athlete. They ignore the fact that common medical conditions make these tests impossible to “pass.” When we look at challenging DUI evidence, we focus heavily on your physical history.

Neurological and Inner Ear Issues

Your balance is controlled by your vestibular system. If you have vertigo, Meniere’s disease, or even a bad cold, your balance will be off. A police officer is not a doctor. They see a stumble and call it impairment. We see a medical reality and call it a false arrest.

Leg, Back, and Joint Injuries

If you have had knee surgery, chronic back pain, or an old ankle injury, you cannot be expected to walk a straight line or stand on one leg. Under state law, the prosecution must prove you were actually impaired. An injury provides a clear, sober explanation for poor physical performance.

Environmental Factors in San Bernardino County

The location of your stop matters just as much as your physical condition. San Bernardino County is known for uneven terrain and heavy traffic.

• Uneven Ground: Roadside surfaces are rarely flat. Dirt, gravel, or a sloped shoulder on the I-10 can make balance exercises impossible
• Passing Traffic: The wind blast from cars traveling at 70 mph creates significant physical force. It also creates a massive distraction
• Flashing Lights: Strobe nystagmus is a real phenomenon. If the officer leaves their patrol lights flashing while doing the eye test, the lights themselves can cause your eyes to jerk
• Inappropriate Footwear: High heels, work boots, or flip-flops are not suitable for balance tests. Officers are supposed to give you the option to remove your shoes, but they rarely do

The Subjective Problem: Officer Bias

Field sobriety tests are not graded by a machine. They are graded by a human being who has already decided you are likely guilty. This is why the officer’s training is so critical. During cross-examination, we often find that officers cannot even name the clues they are supposed to be looking for.

We once had a DMV hearing where the officer made up his own clues. He did not know the validating clues for the HGN or how many were needed to suggest impairment. If an officer does not follow the NHTSA guidelines exactly, the test’s scientific reliability is compromised. We hold them accountable for every error.

California Law and Your Right to Refuse

It is a common myth that you have to perform these physical tests. In California, field sobriety tests are voluntary. You will not find a statute in the California Vehicle Code that says you must perform the Walk and Turn or One Leg Stand.

Please note that this is different from the chemical test (breath or blood) after you are arrested. Under California Vehicle Code Section 23612, you have implied consent to a blood or breath test if you are lawfully arrested for a DUI. But the roadside physical tests? You can say no. Refusal might lead to an arrest, but it prevents the officer from gathering evidence intended to make you look bad.

Aggressive DUI Defense You Can Trust

We represent the falsely accused. We have spent over a decade tearing down the drunk driving myths that the police and prosecutors rely on. We stay informed so we can protect folks in both criminal courts and DMV proceedings. When an officer gets on the stand and tries to act like a balance expert, we are the ones who show the jury they are nothing more than someone who skipped class.

If you have been arrested in Redlands or anywhere in San Bernardino County, you need a team that knows how to win. We do not just look at your BAC; we look at every single second of the officer’s interaction with you. We find the mistakes, we find the bias, and we fight for your future.

Contact Patrick Silva, Attorneys at Law, today at 909-500-4819 for a free consultation. We are ready to put our training to work for you.