Challenging Breathalyzer Results in Chicago DUI Criminal Cases

Law Offices of David L. Freidberg, P.C.

In Chicago, driving under the influence (DUI) is a serious offense that can result in significant legal consequences. One of the primary tools used in DUI arrests is the breathalyzer test, which measures blood alcohol content (BAC). However, breathalyzer results are not infallible and can be challenged in court. Understanding the intricacies of challenging these results can be crucial for those accused of DUI.

Understanding the Role of Breathalyzer Tests in DUI Arrests

In Illinois, DUI laws are primarily governed by 625 ILCS 5/11-501, which defines the offense and outlines penalties. The statute specifies that driving with a BAC of 0.08% or higher constitutes per se impairment. Breathalyzer tests are employed to provide evidence of a driver’s BAC at the time of the arrest.

Breathalyzer results are a critical component in DUI cases because they provide a purportedly scientific measurement of a driver’s impairment. However, the accuracy of these results can be affected by a variety of factors, which can be exploited in a legal defense.

Penalties for DUI in Illinois

A conviction for DUI in Chicago can lead to severe penalties, including:

  • First Offense: Class A misdemeanor, up to one year in jail, fines up to $2,500, and a minimum one-year driver’s license revocation.
  • Second Offense: Class A misdemeanor, mandatory minimum imprisonment of five days or 240 hours of community service, and a five-year license revocation for a second conviction within 20 years.
  • Subsequent Offenses: Class 2 felony, possible imprisonment of 3-7 years, and a ten-year license revocation.

Given these harsh penalties, it is crucial to challenge the validity of breathalyzer results if there is reason to believe they are inaccurate.

The Arrest and Testing Process

DUI Stop and Initial Screening

The process typically begins with a traffic stop, where an officer may conduct field sobriety tests if they suspect alcohol impairment. If these tests suggest intoxication, a breathalyzer test is often administered.

Administering the Breathalyzer

Breathalyzer tests should be performed according to strict protocols to ensure accuracy. The device must be properly calibrated and maintained, and the test must be administered by a qualified individual. Failure to meet these standards can compromise the results.

Processing and Chemical Testing

Following a DUI arrest, further processing includes formal booking and additional chemical testing, which might include blood tests or a second breath test at the station. These results are used to corroborate the initial breathalyzer findings.

The Criminal Case Process

Initial Court Appearance and Arraignment

The accused will be formally charged and asked to enter a plea. This initial phase is crucial for setting the tone of the defense.

Discovery and Evidence Examination

The defense has the right to review all evidence against the accused, including data on the breathalyzer device’s calibration and maintenance records.

Pre-Trial Motions

These might include motions to suppress evidence based on faulty breathalyzer results or improper administration of the test.


During the trial, both the prosecution and defense will present their cases. Challenging the breathalyzer results effectively can be pivotal to the defense.

Challenging Breathalyzer Results

Calibration and Maintenance Issues

Demonstrating that the breathalyzer was improperly calibrated or poorly maintained is a strong defense. Inaccuracies in calibration can lead to falsely high BAC readings.

Operator Error

The qualifications of the operator and the procedure followed during the test can also be grounds for challenging the results. Any deviation from standard protocols can affect the test’s reliability.

Medical and Dietary Factors

Certain medical conditions and diets can affect breathalyzer results. For instance, individuals with diabetes or those on high-protein, low-carbohydrate diets might produce substances that can be mistakenly detected as alcohol by breathalyzers.

Call Attorney Freidberg For Your Free Consultation

If you face DUI charges in Chicago and believe the breathalyzer results used against you are flawed, securing experienced legal representation is critical. The Law Offices of David L. Freidberg understand the complexities of DUI cases and are adept at challenging breathalyzer evidence. With our detailed knowledge of legal standards and defense strategies, we are committed to ensuring the best possible outcome for our clients.

Do not let a DUI charge define your future. Contact us 24/7 at (312) 560-7100 or toll-free at (800) 803-1442 for a free consultation. Serving clients across Chicago and surrounding counties, we are here to help you navigate through this challenging time with confidence and legal expertise.

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