Field Sobriety Tests in Illinois
Field sobriety tests are the gateway to a DUI arrest in Illinois. Roadside performance, often on poor footing, in poor lighting, after midnight, in shoes never meant for a balance test, frequently determines whether a driver goes home or to the police station. The tests are designed for a specific use under specific conditions, and the conditions are rarely met. A Chicago DUI lawyer reviewing your case looks first at how the field sobriety tests were administered. Call (888) 828-2305 for a free 24/7 consultation.
The NHTSA Standardized Three-Test Battery
The National Highway Traffic Safety Administration developed three tests intended to be administered together. Together, the three tests are designed to give an officer a structured tool for evaluating impairment. The three tests are:
- Horizontal Gaze Nystagmus (HGN). The officer asks the subject to follow a stimulus, typically a pen or fingertip, with their eyes while keeping their head still. The officer looks for involuntary jerking of the eye (nystagmus) as it tracks the stimulus.
- Walk-and-Turn. The subject takes nine heel-to-toe steps along a straight line, turns in a specific way, and takes nine heel-to-toe steps back. The officer scores eight defined clues.
- One-Leg Stand. The subject stands on one leg with the other raised approximately six inches off the ground while counting aloud for 30 seconds. The officer scores four defined clues.
Are Field Sobriety Tests Required in Illinois?
No. Field sobriety tests are voluntary in Illinois. A driver can decline to perform them without triggering the implied consent suspension that applies to refusing the chemical breath or blood test. Declining the field sobriety tests does not eliminate the possibility of arrest, but it does deny the officer one piece of evidence and one set of observations to use later.
Common Challenges to Field Sobriety Test Results
Surface and Environmental Conditions
The NHTSA manual itself specifies that the walk-and-turn and one-leg stand should be administered on a reasonably level, dry, hard, non-slippery surface with adequate room for the subject to perform the test safely. Real-world Chicago roadside conditions rarely meet this standard:
- Gravel shoulders that are not level.
- Snow, ice, or wet asphalt.
- Sloped pavement at the edge of the road.
- Insufficient lighting.
- High winds that affect balance.
- Heavy traffic noise and visual distractions.
Instructions and Demonstration
The NHTSA protocol requires specific verbal instructions and a demonstration before each test. Each instruction must be given. Each part of the demonstration must be performed correctly. A Chicago DUI lawyer reviewing bodycam footage frequently identifies skipped or rushed instructions that invalidate the test.
Subject Characteristics
The NHTSA validation studies were conducted on subjects within specific characteristics. The studies do not necessarily apply to subjects outside those parameters:
- Subjects over 65.
- Subjects more than 50 pounds overweight.
- Subjects with back, knee, leg, or balance conditions.
- Subjects with inner ear problems or vertigo.
- Subjects with neurological conditions affecting eye movement.
- Subjects wearing footwear with more than 2-inch heels (should be offered the opportunity to remove).
What HGN Actually Measures and Doesn't Measure
Horizontal Gaze Nystagmus is the most scientific-seeming of the three tests, but it is also the most challengeable. Nystagmus is involuntary eye jerking that can be caused by alcohol, but it can also be caused by:
- Medical conditions including diabetes, certain neurological conditions, inner ear infections, and head injuries.
- Medications including some prescription drugs unrelated to alcohol.
- Caffeine, nicotine, and over-the-counter cold medications in some subjects.
- Fatigue and circadian rhythm effects.
- Eye strain or vision conditions.
The officer typically cannot administer the HGN properly without specific training and a controlled stimulus. Improperly held stimulus, wrong speed, wrong distance, or wrong angle all invalidate the test. Illinois courts have addressed HGN admissibility extensively, and the foundation requirements are stricter than the average officer's testimony usually provides.
What Walk-and-Turn and One-Leg Stand Actually Measure
Both tests are divided attention tests. They require the subject to focus on multiple tasks simultaneously: physical balance, counting, listening, remembering instructions. The premise is that alcohol impairs divided attention. The reality is that many sober people fail divided attention tests, particularly:
- People who are nervous, frightened, or anxious (the typical state of a person being investigated for DUI).
- People who have been awake for many hours.
- People who are recovering from any minor injury.
- People with athletic injuries, prior surgeries, or chronic pain.
- People who are physically deconditioned.
Scoring and What Officers Look For
The NHTSA protocol identifies specific "clues" for each test:
- HGN: 6 clues (3 per eye); 4 or more indicates likely impairment.
- Walk-and-Turn: 8 clues; 2 or more indicates likely impairment.
- One-Leg Stand: 4 clues; 2 or more indicates likely impairment.
The scoring system is structured, but the officer's observations are subjective. Bodycam review often reveals clues that were scored when they should not have been, or actions that the officer interpreted as clues but are visible only ambiguously on the video.
Non-Standardized Field Sobriety Tests
Some officers also administer non-standardized tests: the alphabet test, finger-to-nose, finger count, Romberg balance test, and others. These tests have no NHTSA validation and no defined protocol. Their reliability is significantly lower than the three-test battery. Performance on non-standardized tests is open to wide-ranging challenge.
Related Pages
- Breathalyzer test - chemical test procedure.
- Breath evidence - breath evidence challenges.
- Blood evidence - blood evidence challenges.
- DUI evidence - all evidence types.
- DUI defense arguments - defense strategy overview.
Free 24/7 Consultation
Field sobriety challenges are detailed and require careful video review. Call (888) 828-2305 now for a free consultation with a Chicago DUI lawyer. Available 24 hours a day, seven days a week.