Field Sobriety Tests Aren’t Foolproof
If you've been arrested for DUI in Tucson or Pima County, chances are you were asked to perform field sobriety tests (FSTs) during the stop. These tests are supposed to help officers determine whether a driver is impaired. However, FSTs are far from perfect, and they are often conducted in conditions that make them unreliable and misleading. Just because an officer performs an FST doesn't mean the results are valid or accurate.
As an experienced Tucson DUI defense attorney at AJB Law Firm, LLC, I have seen how unreliable FST results can unfairly impact my clients. Whether it’s the Horizontal Gaze Nystagmus (HGN) test performed amid passing traffic, a Walk-and-Turn (WAT) test on an uneven surface, or a seated test based on outdated protocols, the reality is that these tests are often prone to error. In this post, I'll break down why FSTs aren’t foolproof, the problems with how they're administered, and how to challenge them effectively in court.
Understanding Standardized and Non-Standardized Field Sobriety Tests
The National Highway Traffic Safety Administration (NHTSA) has approved three standardized field sobriety tests:
Horizontal Gaze Nystagmus (HGN): Detects involuntary jerking of the eyes, which may indicate intoxication.
Walk-and-Turn (WAT): Tests balance, coordination, and the ability to follow instructions.
One-Leg Stand (OLS): Measures balance and motor control.
However, officers sometimes use non-standardized tests, such as the Finger-to-Nose Test, Palm Pat Test, or Hand Coordination Test. These are not validated by NHTSA and can be highly subjective and prone to misinterpretation.
Why Non-Standardized Tests Are Problematic
The issue with non-standardized tests is that they lack consistency and reliability. Officers may claim that they are assessing coordination or balance, but there are no uniform criteria for scoring these tests. Moreover, many of these tests were originally designed for boating under the influence (BUI) assessments under the National Association of State Boating Law Administrators (NASBLA), not for roadside DUI investigations.
One of the most concerning aspects of these non-standardized tests is that they introduce more bias than they eliminate. An officer’s perception of how someone performs a non-standardized test is highly subjective and often influenced by preconceived notions about intoxication.
Problems with the Horizontal Gaze Nystagmus (HGN) Test
The HGN test is one of the most commonly administered FSTs. It involves observing the eyes for involuntary jerking movements, or nystagmus, as the person follows a moving object. While NHTSA claims the test is scientifically valid, there are numerous reasons why HGN results can be unreliable:
Peripheral Vision Distractions: If moving objects are visible in the subject’s peripheral vision, the eyes may naturally follow those objects, creating false positives for nystagmus.
Environmental Factors: Wind, cold, or even stress can make a person's eyes water, further complicating the assessment.
Medical Conditions: Certain medical issues, like neurological disorders or inner ear problems, can cause nystagmus without alcohol consumption.
Why the Walk-and-Turn (WAT) and One-Leg Stand (OLS) Tests Are Flawed
These tests are designed to assess balance and coordination, but they were developed under ideal conditions—flat, well-lit surfaces, without wind or noise. Real-world scenarios rarely meet these criteria. Issues with these tests include:
Uneven Terrain: Conducting the Walk-and-Turn on an uneven or slippery surface can result in false indications of impairment.
Medical Issues: Conditions like arthritis or past injuries can impair balance even when a person is completely sober.
Fatigue and Anxiety: Stress and fatigue can affect coordination, especially during a late-night stop after a long day.
The Dangers of Seated Field Sobriety Tests
In some cases, officers conduct seated FSTs, such as the Finger-to-Nose Test or the Palm Pat Test. These tests were originally created for boating situations, where performing standing tests on a rocking boat is impractical. Applying these tests to DUI stops on the roadside is problematic for several reasons:
Different Testing Standards: These tests are not recognized or standardized by NHTSA for DUI enforcement.
Subjectivity and Lack of Validation: There is no standardized scoring system, making the results inherently unreliable.
Inconsistent Training: Officers may not receive adequate training on how to properly administer and interpret these tests, leading to inconsistent applications.
Real-World Example: Dismissing FST Evidence in Court
In one of my recent cases, the officer conducted both standardized and non-standardized tests on my client in the middle of a busy highway. The client was subjected to the HGN test while cars sped by, creating distracting motion in the peripheral vision. The officer also performed a Palm Pat Test while the client sat on the curb with uneven ground.
During cross-examination, I challenged the officer’s interpretation of the results, pointing out the environmental distractions and the lack of scientific validation for non-standardized tests. The judge agreed that the field conditions were not conducive to reliable testing and ruled that the FST results were inadmissible as evidence.
Challenging FST Results in Court
If you’ve been arrested for DUI based on FST results, it is crucial to challenge the validity of those tests. An experienced attorney can:
Review body-worn camera footage to assess the environmental conditions.
Cross-examine the officer to expose inconsistencies and flawed procedures.
Present expert testimony on why the tests were not reliable under the given circumstances.
Why You Need an Experienced Tucson DUI Attorney
Field sobriety tests are often the cornerstone of a DUI arrest, but they are not always reliable. Don’t assume that just because an officer administered a test that it was done correctly or that the results are valid. At AJB Law Firm, LLC, I am committed to fighting for my clients by challenging unreliable tests and holding law enforcement accountable. Contact me today to discuss your case and how we can fight your DUI charges.
