What Evidence Law Enforcement Looks for in DUI Cases in Chicago, Illinois

Driving under the influence (DUI) charges in Chicago are aggressively pursued by law enforcement. Whether you’re pulled over on Lake Shore Drive or stopped in a Cook County suburb like Cicero or Oak Park, an officer will be trained to look for specific signs and gather various forms of evidence to justify an arrest. In Illinois, DUI can be charged as a misdemeanor or a felony depending on the circumstances. For those accused, understanding what evidence police look for—and how to defend against it—is essential. At The Law Offices of David L. Freidberg, we’ve spent decades fighting DUI charges across Cook County, DuPage County, Will County, and Lake County.

How DUI Charges Begin in Illinois and the Categories of Offense

A DUI arrest in Illinois usually begins with a traffic stop. Law enforcement may claim they observed improper lane usage, speeding, failure to signal, or another violation. In some cases, a DUI investigation starts at the scene of an accident or during a DUI checkpoint operation.

Under Illinois law, driving under the influence is defined by 625 ILCS 5/11-501, which prohibits operating a motor vehicle:

With a blood alcohol concentration (BAC) of 0.08 or higher
While under the influence of alcohol, drugs, or a combination that impairs driving
With any amount of a controlled substance in the driver’s system

First and second offenses are typically charged as Class A misdemeanors. A third DUI, or a DUI involving aggravating factors—such as serious bodily injury, death, or driving without a license—can result in felony charges under 625 ILCS 5/11-501(d).

Convictions carry severe consequences. For a misdemeanor DUI, you could face up to 364 days in jail, a $2,500 fine, license suspension, alcohol education classes, and mandatory use of a breath alcohol ignition interlock device (BAIID). Felony DUIs carry years in prison and permanent damage to your criminal record.

For more on DUI charges in Illinois, see our legal blog here:
https://www.chicagocriminallawyerblog.com

Types of Evidence Police Look for in DUI Investigations

Law enforcement officers in Chicago and throughout Illinois are trained to gather a wide range of evidence during DUI investigations. Much of this evidence is subjective, and that’s why it’s important to understand how this information is collected and how it may be challenged.

The most common forms of DUI evidence include:

Officer Observations
The first piece of evidence typically involves the officer’s visual and behavioral observations. Police are trained to look for indicators such as slurred speech, red or bloodshot eyes, the smell of alcohol, fumbling when producing identification, or difficulty exiting the vehicle. These observations are often recorded in police reports and can be introduced in court testimony.

Field Sobriety Tests (FSTs)
These standardized tests, developed by the National Highway Traffic Safety Administration (NHTSA), include the horizontal gaze nystagmus test, the walk-and-turn, and the one-leg stand. Officers administer these tests to evaluate a driver’s coordination, balance, and ability to follow directions. But these tests are not always accurate. Weather conditions, medical conditions, poor footwear, and anxiety can all lead to poor performance.

Preliminary Breath Test (PBT)
Police may ask drivers to blow into a handheld breathalyzer at the roadside. While the PBT results are typically inadmissible in court to prove intoxication, they can be used to establish probable cause for arrest.

Chemical Testing
After an arrest, Illinois law requires drivers to submit to breath, blood, or urine testing at a police station or medical facility. Under the Illinois Implied Consent Law (625 ILCS 5/11-501.1), refusal to submit to testing results in a statutory summary suspension of driving privileges, even if the driver is later found not guilty of DUI.

Video Evidence
Squad car dashcams and police body cameras are often active during the stop. These videos may include the initial traffic stop, the conversation with the officer, field sobriety testing, and the arrest. In some cases, this footage contradicts the officer’s written report and helps the defense.

Witness Statements and Accident Evidence
In DUI cases involving accidents, police will often collect witness statements and investigate whether intoxication played a role. Skid marks, vehicle damage, and photos may be used to support the prosecution’s case.

To learn more about how DUI evidence is challenged, visit our main site:
https://www.chicagocriminallawyer.pro

The Criminal Case Process in Illinois and the Importance of a Defense Attorney

Every DUI case in Illinois follows a process that begins with arrest and ends with resolution through trial or plea. Without skilled legal guidance, each stage presents risks for the accused.

Arrest and Booking
After a DUI arrest, the defendant is taken to the local police department or jail, processed, and held pending bond. If a chemical test showed a BAC of 0.08 or higher, or if the driver refused testing, a statutory summary suspension of driving privileges begins 46 days later unless challenged.

First Court Appearance and Preliminary Hearing
This appearance gives the judge an opportunity to advise the defendant of the charges and set future court dates. A defense attorney can file motions, challenge evidence, and even request a hearing to contest the summary suspension.

Pretrial Motions and Discovery
Attorneys can request discovery (police reports, videos, test results) and file motions to suppress unlawfully obtained evidence. For instance, if the traffic stop was made without probable cause, any evidence gathered may be excluded.

Trial or Plea Negotiation
In many cases, a trial is avoided through effective plea bargaining. But when necessary, we proceed to trial and present a full defense, challenging the evidence and confronting the arresting officers.

A criminal defense attorney is essential to protect your rights during every step. Without an advocate, you risk conviction, license loss, and a permanent record that affects your job, education, housing, and reputation.

Real Case Example: Defending a Client with a High BAC Result

One of our clients was charged with DUI after a late-night stop near Wrigleyville. The officer alleged that the driver was swerving and smelled of alcohol. Field sobriety tests were conducted on uneven pavement, and the driver submitted to a breath test that registered 0.12 BAC.

We challenged the initial stop by showing dashcam footage that contradicted the officer’s claim of improper lane usage. We also retained a toxicology expert to examine the breathalyzer calibration logs, which revealed improper maintenance. The court granted our motion to suppress the breath test. Without that evidence, the prosecution offered a reduced charge that avoided jail time and license suspension.

This case shows how strategic legal defense can neutralize damaging evidence.

Legal Defenses to DUI Charges in Illinois

The best defense depends on the circumstances of each case, but common DUI defenses in Illinois include:

Lack of Reasonable Suspicion for Stop: If the traffic stop was unlawful, all subsequent evidence may be inadmissible.
Improper Field Sobriety Test Administration: Officers often fail to follow NHTSA guidelines, making test results unreliable.
Invalid Breathalyzer Results: These machines require regular calibration and proper use; errors can compromise results.
Medical Conditions or Fatigue: Symptoms mistaken for intoxication may be due to health issues or lack of sleep.

An experienced defense lawyer will analyze the details of your case and identify which defense applies best to protect your rights and your future.

Choosing the Right Criminal Defense Attorney in Illinois

If you are facing DUI charges in Chicago or the surrounding counties, you need a defense attorney who understands the local courts, prosecutors, and police tactics. You should look for someone who has a proven track record with DUI cases, a deep understanding of Illinois law, and courtroom experience.

During your free consultation, ask the following:

How many DUI cases have you handled?
What defenses have you successfully used in past cases?
Can you help fight the statutory summary suspension?
Do you regularly appear in Cook County courts?

Choosing the right lawyer may mean the difference between jail time and dismissal, between losing your license and keeping your job.

Why You Shouldn’t Face DUI Charges Alone

Illinois prosecutors take DUI cases seriously, and they are under pressure to pursue harsh penalties to deter impaired driving. Trying to handle a case on your own is risky, especially when you’re up against trained police officers, state-funded labs, and prosecutors with extensive resources.

The Law Offices of David L. Freidberg has decades of experience representing clients charged with DUI in Chicago, Cook County, and surrounding jurisdictions. We know what law enforcement is looking for—and we know how to challenge it.

Frequently Asked Questions – DUI Charges in Chicago, Illinois

What happens if I refuse a breath test in Illinois?
Refusing a chemical test after arrest leads to an automatic suspension of your driver’s license under Illinois’s implied consent law. The suspension lasts one year for a first offense and three years for a second. However, refusal may limit the evidence available to the prosecution.

Can I beat a DUI if I failed the breathalyzer?
Yes, breathalyzer results can be challenged if the device was not properly calibrated or administered, or if the officer was not certified. Other factors like diet, medical conditions, or rising BAC can also affect the result.

How long will a DUI stay on my record in Illinois?
A DUI conviction in Illinois is permanent. It cannot be expunged or sealed, and it will affect your record indefinitely unless the case was dismissed or you were found not guilty.

What is a statutory summary suspension?
This is an automatic suspension of driving privileges triggered by a failed or refused chemical test. It is separate from the criminal DUI charge and begins 46 days after arrest unless contested.

Can I drive after a DUI arrest in Chicago?
You may be eligible for a Monitoring Device Driving Permit (MDDP), allowing you to drive with a BAIID installed. Eligibility depends on your driving record and whether it was a first offense.

Do I need a lawyer for a first-time DUI?
Absolutely. A first offense still carries jail time, heavy fines, and license suspension. With legal help, you may be able to avoid a conviction or reduce the consequences.

Choose The Law Offices of David L. Freidberg to Defend Your DUI Case

A DUI arrest can change your life, but you are not alone. The evidence collected against you is not unbeatable. At The Law Offices of David L. Freidberg, we fight to suppress evidence, protect your rights, and keep your record clean. Whether you’re in Cook County, DuPage County, Will County, or Lake County, we are available 24/7 to defend your case.

Call The Law Offices of David L. Freidberg now at (312) 560-7100 or toll-free at (800) 803-1442 for your free consultation.

We’re here when you need us—24 hours a day, 7 days a week.

Call The Law Offices of David L. Freidberg Today

If you’re under investigation or facing charges, act now. The prosecution is already building a case. You deserve a defense that’s prepared to challenge the legality of every move law enforcement made.

Contact us today at (312) 560-7100 or toll-free at (800) 803-1442 for a free consultation. We’re available 24/7 to serve clients throughout Illinois, Cook County, DuPage County, Will County, and Lake County.

You don’t have to face this alone—we’re here to fight for you.