Chicago Breathalyzer Test
The breathalyzer is the central piece of chemical evidence in most Illinois DUI cases. Officers commonly use two distinct types of breath tests during a Chicago DUI investigation: a roadside Portable Breath Test (PBT) and a station-based evidentiary breath test. The two have very different legal weight, different procedural requirements, and different challenge opportunities. If you took or refused a breathalyzer test in connection with a Cook County DUI arrest, call (888) 828-2305 for a free 24/7 consultation with a Chicago DUI lawyer.
The Roadside Portable Breath Test
The PBT is a small handheld device the officer may offer to use during the traffic stop, before any arrest decision. The PBT serves a narrow legal purpose: it gives the officer one more piece of information for the probable cause determination. It is not admissible at trial to prove BAC. It is admissible only for the limited purpose of probable cause review at a suppression hearing.
The PBT is voluntary in Illinois. A driver can refuse the PBT without triggering the implied consent suspension that applies to the station test. Refusing the PBT does not increase or decrease the criminal exposure, but it does remove one piece of evidence from the probable cause calculation. Whether refusing makes sense depends on the specific situation; in most cases, declining the roadside PBT is the more conservative choice.
The Station Evidentiary Breath Test
The evidentiary breath test is the one that matters for the criminal case and the Statutory Summary Suspension. It is administered at the police station on an approved instrument by a certified operator following the procedure required by 20 Illinois Administrative Code Section 1286.
The Test Procedure
- The subject is transported to the testing location and held there.
- The operator conducts a 20-minute observation period during which the subject cannot eat, drink, smoke, vomit, regurgitate, or have anything in their mouth.
- The operator runs the instrument through its startup procedure, including ambient air checks.
- The subject blows two samples into the mouthpiece, producing a deep lung air sample of sufficient volume.
- The instrument prints a result showing both samples, the time of each, and the calculated BAC.
Refusing the Station Breath Test
Illinois implied consent law treats refusal of the station breath test as a separate matter from the underlying DUI charge. Refusal triggers an automatic Statutory Summary Suspension:
- First refusal: 1 year suspension.
- Second refusal within 5 years: 3 year suspension.
The refusal suspension takes effect on day 46 after the arrest unless the driver requests a hearing within 90 days. See our Secretary of State information page for hearing procedures.
Refusal also tells the prosecution they need a warrant to obtain blood evidence. In serious cases involving accidents or injuries, prosecutors and officers typically pursue a warrant. The refusal does not block the prosecution from getting chemical evidence; it just changes the path.
Common Breathalyzer Challenges
The 20-Minute Observation Period
The observation period requirement is one of the most violated and most successfully challenged elements. Bodycam review often shows the officer was distracted, the subject moved an object in their mouth, or the period actually started later than the log indicates. A successful observation period challenge often results in suppression of the breath result.
Calibration and Maintenance Records
Illinois requires instruments to be calibrated and certified on a defined schedule using simulator solutions of known concentration. Calibration records are subject to discovery. A Chicago DUI lawyer routinely subpoenas:
- The instrument's calibration logs for the period before and after the test.
- Records of any maintenance, repair, or adjustment to the instrument.
- Simulator solution certifications and expiration dates.
- The certification records of the personnel performing the calibration.
Operator Certification
The Breath Analysis Operator must be certified at the time of the test. Certification documents and any lapses are subject to discovery and challenge.
Instrument Error Codes
Breathalyzers log internal events including error codes, aborted tests, and out-of-range results. Errors in the logs near the time of the suspect's test can call the result into question.
Mouth Alcohol Sources
Belching, regurgitation, recent ingestion, certain medications, oral piercings, and conditions like GERD can all produce mouth alcohol artifacts that elevate the apparent BAC. See our breath evidence page for the full list.
Breath Temperature
The standard breath temperature assumption used by the instrument may not match the subject's actual breath temperature. Variation can shift the reading by 6 to 8 percent per degree Celsius.
Should I Take the Breathalyzer Test?
The decision to take or refuse the breath test is a personal one with significant consequences either way. Some considerations:
- If you take the test and pass below .08, the BAC component of the DUI prosecution is removed. The case may still proceed on observation evidence, but the strongest prosecution evidence is gone.
- If you take the test and fail, the BAC becomes part of the case, but the suspension is shorter (6 months if under 5,000 prior driving privileges).
- If you refuse, no BAC is in evidence directly, but the suspension is longer (1 year first refusal, 3 years subsequent).
- If you refuse, the prosecution may pursue a warrant for blood. Whether they do depends on the seriousness of the case.
This is not legal advice for any specific situation. A Chicago DUI lawyer who knows the specific facts of your stop and arrest can advise on the implications of either choice.
Related Pages
- Breath evidence - detailed evidence challenges.
- Blood evidence - blood testing protocol.
- Field sobriety test - roadside tests preceding breath testing.
- DUI defense arguments - full defense strategy.
- Secretary of State information - suspension hearings.
Free 24/7 Consultation
Breathalyzer challenges require specific discovery and aggressive motion practice. Call (888) 828-2305 for a free consultation with a Chicago DUI lawyer. The line is open 24 hours a day, seven days a week. Evidence preservation begins when you call.