Field Sobriety Test Defense in Cook County

Field sobriety tests are subjective, frequently misadministered, and often wrong. Former prosecutors know how to tear them apart.

Field Sobriety Tests Designed to Fail — Not to Find the Truth

Here's what police don't tell you: field sobriety tests are designed to generate evidence against you, not to determine whether you're actually impaired. Even when administered perfectly — which they rarely are — these tests have significant error rates. Even sober people fail them regularly.

The three "Standardized Field Sobriety Tests" validated by NHTSA are the Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand. Officers use them as if they're scientific instruments, but the reality is far different. They're highly subjective, easily affected by conditions unrelated to alcohol, and frequently administered incorrectly.

As former prosecutors, we relied on field sobriety test evidence to build DUI cases. We know how officers are trained, how the tests are supposed to be administered, and what deviations render results unreliable. Now we use that same knowledge to challenge FST evidence and protect our clients from wrongful conviction.

The Three Tests Understanding Standardized Field Sobriety Tests

Horizontal Gaze Nystagmus (HGN)

The officer moves an object before your eyes, looking for involuntary jerking. But nystagmus can be caused by medical conditions, medications, caffeine, and fatigue — not just alcohol. Even properly administered, this test is only 77% accurate.

Walk-and-Turn

Walk heel-to-toe along a line, turn, and walk back. Officers look for losing balance, wrong number of steps, or failing to touch heel-to-toe. Uneven surfaces, improper footwear, weight, age, and nerves all affect performance. Only 68% accurate.

One-Leg Stand

Balance on one foot for 30 seconds while counting. Officers watch for swaying, hopping, or putting the foot down. Inner ear problems, leg injuries, age, obesity, and anxiety can all cause failure. Just 65% accurate.

Combined Accuracy

Even when all three tests are combined and administered perfectly, NHTSA's own research shows accuracy of only 82%. That means nearly 1 in 5 people fail these tests even when completely sober. These odds are unacceptable for criminal prosecution.

Defense Strategies How We Challenge Field Sobriety Evidence
Protocol Violations

NHTSA protocols require specific instructions, demonstration, and scoring. We review dashcam and bodycam footage to identify deviations. Improperly administered tests lose their scientific validity.

Environmental Factors

Tests must be conducted on flat, dry, well-lit surfaces. Wind, rain, cold, darkness, uneven pavement, and traffic distractions all affect performance. We document conditions that make test results unreliable.

Physical/Medical Conditions

Age, weight, injuries, inner ear conditions, medications, and natural lack of coordination all cause test failures unrelated to alcohol. We identify and present alternative explanations for poor performance.

Officer Training Gaps

Not all officers are properly trained in NHTSA protocols. We examine training records and certifications. An officer who doesn't fully understand the tests can't reliably interpret results.

FAQ Field Sobriety Tests — Frequently Asked Questions

The three NHTSA-validated Standardized Field Sobriety Tests are: Horizontal Gaze Nystagmus (HGN), Walk-and-Turn, and One-Leg Stand. Officers use these to assess impairment, but they are highly subjective, have significant error rates, and are often improperly administered.

Yes. Unlike breath tests, field sobriety tests are voluntary in Illinois. You can politely decline to perform them without triggering enhanced license penalties. Many defense attorneys recommend declining because these tests are designed to generate evidence against you, not to prove your innocence.

Even when administered correctly, NHTSA research shows HGN is only 77% accurate, Walk-and-Turn 68% accurate, and One-Leg Stand 65% accurate. When combined, accuracy improves to only 82%. This means nearly 1 in 5 people fail these tests even when completely sober.

Many factors cause false failures: age over 65, inner ear conditions, leg or back injuries, obesity, certain medications, footwear (especially heels), uneven surfaces, weather conditions, anxiety, and even being naturally uncoordinated. These medical conditions and environmental factors are often ignored by officers.

We examine whether NHTSA protocols were followed precisely, whether environmental conditions were appropriate, whether instructions were clear, and whether the officer is properly trained. We also identify medical conditions or other factors that explain poor performance without impairment.

Failed Field Sobriety Tests? They Don't Tell the Whole Story.

These tests are designed to make people fail. Let former prosecutors expose the flaws. Free consultation. ¡Se habla español!

Call 847-520-4810 Now
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