Field sobriety tests (FSTs) are roadside exercises used by Illinois police to assess impairment during DUI stops, but they're far from foolproof—factors like weather, medical conditions, or nervousness can lead to false positives and unjust arrests. As a Joliet DUI attorney with over 20 years of experience, including my time as a former Will County prosecutor, I've challenged countless FST results to secure dismissals, reductions, or acquittals for clients.
At the Law Office of Jack L. Zaremba, we scrutinize these tests in Will County courts, where officers on I-80 or local roads often rely on them for probable cause. In this blog post, we'll cover common FSTs under Illinois law, their limitations in 2026, penalties for failing, and proven defense strategies. For related topics, see our guide on challenging breathalyzer results .
What Are Field Sobriety Tests in Illinois DUI Stops?
Field sobriety tests are standardized physical and cognitive tasks administered by officers to detect signs of alcohol or drug impairment before a chemical test. Under Illinois guidelines (aligned with NHTSA standards), refusal isn't mandatory but can imply consciousness of guilt in court.
In Will County, Joliet stops frequently involve FSTs during nighttime patrols or checkpoints, providing probable cause for arrest if "failed"—though they're subjective and not always recorded on body cams in 2026.
Common Types of Field Sobriety Tests and Their Reliability
Standardized FSTs include:
- Horizontal Gaze Nystagmus (HGN): Officer tracks eye movements for jerking—claimed 88% accurate but affected by medical issues or lighting.
- Walk-and-Turn: Nine heel-to-toe steps, turn, and return—tests balance but unreliable on uneven surfaces or for those with injuries.
- One-Leg Stand: Balancing on one leg for 30 seconds—impacted by age, weight, or fatigue.
Non-standardized tests like alphabet recitation may also be used. In 2026, increased body cam usage helps challenge administration errors.
Penalties for Failing Field Sobriety Tests in a DUI Case
Failing FSTs often leads to arrest and DUI charges: Class A misdemeanor for first offenses (up to 364 days jail, $2,500 fines), with license suspension, probation, treatment, and insurance hikes. Aggravated factors (e.g., high BAC / Child / Injuries) escalate to felonies.
Will County consequences include statutory summary suspension (6-12 months), BAIID requirements, and records affecting jobs—especially CDL holders.
Defense Strategies Against Field Sobriety Test Results
FSTs are defensible due to subjectivity:
- Challenge Administration: Argue improper instructions, poor conditions, or officer bias.
- Medical/Physical Explanations: Provide evidence of conditions mimicking impairment (e.g., inner ear issues).
- Lack of Video Evidence: Suppress if no recording or discrepancies.
- Expert Testimony: Use specialists to debunk reliability.
- Negotiate Alternatives: Reduce to reckless driving for supervision.
In Joliet courts, we've dismissed cases by exposing FST flaws.
Why Hire a DUI Attorney Experienced with Field Sobriety Tests?
FST challenges require legal expertise to suppress evidence and negotiate. As a former prosecutor, I know Will County tactics, delivering results that protect your license and record.
Facing DUI charges involving field sobriety tests in Will County? Contact the Law Office of Jack L. Zaremba for a free, confidential consultation. Visit our contact page or call our Joliet office to defend your case in 2026. Act now—strong defenses start early.
