Illinois DUI Laws Explained

By Javier Marín, Editor·Last reviewed September 2026·How we check this

An Illinois DUI arrest sets two tracks running at the same time: a criminal case under 625 ILCS 5/11-501 in the Circuit Court, and a civil Statutory Summary Suspension imposed by the Secretary of State. The civil track moves faster — the suspension begins on day 46 — so most defense work happens in the first six weeks after arrest.

The legal threshold

Adults 21+: 0.08% BAC.
Drivers under 21: any detectable amount of alcohol (zero tolerance under the Use/Lose law).
Commercial drivers: 0.04% BAC while operating a commercial vehicle.
School bus drivers: 0.04% BAC.
Drivers on DUI probation: 0.05% BAC.

Illinois also recognizes Driving While Under the Influence of Drugs — any amount of cannabis above 5 nanograms in whole blood or 10 nanograms in oral fluid, plus any controlled substance not validly prescribed.

Statutory Summary Suspension

The Statutory Summary Suspension is automatic and civil — it does not depend on a criminal conviction. The arresting officer issues a notice at the scene; the suspension begins on the 46th day after arrest:

6 months for a first failed chemical test (BAC 0.08% or higher, or any controlled substance).
12 months for a first chemical-test refusal.
1 year for a subsequent failed test within 5 years.
3 years for a subsequent refusal within 5 years.

Petition to rescind

Within 90 days of the arrest, the defendant can file a Petition to Rescind in Circuit Court that, if granted, undoes the suspension. The petition addresses four narrow issues: did the arresting officer have reasonable grounds, was the driver properly arrested, was the driver warned of the consequences of refusing, and did the chemical test show 0.08% or higher. Winning the petition does not affect the criminal case but does prevent the civil suspension.

First-offense criminal penalties

A first-offense Illinois DUI conviction is a Class A misdemeanor with these typical consequences:

Up to 364 days in county jail (rarely imposed for a first offense without aggravating factors).
Up to $2,500 in fines, plus court costs and DUI Equipment Fund assessments that often add $1,000 more.
A 1-year license revocation (separate from and on top of the Statutory Summary Suspension).
Mandatory completion of a state-licensed alcohol/drug evaluation and treatment program.
Victim Impact Panel attendance.
BAIID installation on the offender's vehicle as a condition of an MDDP permit.
SR-22 insurance filing for at least 3 years.

Monitoring Device Driving Permit (MDDP)

First-time DUI offenders can apply for an MDDP that allows unlimited driving so long as a Breath Alcohol Ignition Interlock Device (BAIID) is installed on every vehicle driven. The device costs $80-$150 a month plus a $100 install fee. Failed BAIID readings are reported to the SOS within 24 hours and can extend the MDDP period.

Aggravating factors

Penalties escalate quickly when any of these apply:

BAC of 0.16% or higher: mandatory 100 hours of community service and $500 minimum fine added.
DUI with a child under 16 in the vehicle: mandatory 6 months in jail plus $1,000 fine and 25 days of community service.
Causing great bodily harm: charged as an Aggravated DUI, a Class 4 felony.
Driving on a previously suspended or revoked license: Aggravated DUI, Class 4 felony.
Causing death: Aggravated DUI, a Class 2 felony with a mandatory 3-14 year prison term.

Repeat offenses

A second DUI is a Class A misdemeanor with a mandatory 5-day jail sentence or 240 hours of community service. A third DUI is a Class 2 felony with a 3-7 year prison range. Illinois does not have a lookback period for DUI priors — every conviction counts toward enhancement, no matter how old.

For a national perspective, see our national DUI guide.