Overview
What Is a Per Se DUI
Under 625 ILCS 5/11-501(a)(1)?
Under Illinois law, a person commits DUI when they drive or are in actual physical control of a motor vehicle with a blood alcohol concentration (BAC) of 0.08% or more in their blood, breath, or other bodily substance. This is codified under 625 ILCS 5/11-501(a)(1) and is called a "per se" DUI.
The word "per se" is critical. It means the BAC number alone is enough to convict. The prosecution does not need to prove that you were actually drunk, that your driving was impaired, or that you were unsafe on the road. If the state can show that a properly administered chemical test produced a result of 0.08% or higher, the legal elements of the offense are met.
This is the most commonly charged DUI offense in Illinois. When a driver submits to a breathalyzer at the station and the result comes back at or above 0.08%, officers will charge the (a)(1) count. In most arrests, this charge is paired with an (a)(2) "under the influence" charge as a backup, giving prosecutors two paths to conviction.
McMahon Law Offices defends clients charged with per se DUI throughout DuPage County, Kane County, and Cook County. As a former prosecutor, Mike McMahon knows exactly how the state builds these cases and where they break down.
Penalties and Consequences
What You Face
If Convicted
A first-offense DUI over 0.08 BAC is a Class A misdemeanor in Illinois. The penalties vary depending on your BAC level, prior history, and whether any aggravating factors are present. Here is the full picture.
Prosecution's Case
How the State Proves
a Per Se DUI Charge
To convict under 625 ILCS 5/11-501(a)(1), the prosecution must prove two elements beyond a reasonable doubt:
1. You were driving or in actual physical control of a vehicle. Driving is straightforward, but "actual physical control" is broader and has been the subject of significant litigation in Illinois. Being found asleep in a parked car with keys in the ignition can qualify.
2. Your BAC was 0.08% or higher. This must be established through a chemical test of your blood, breath, or other bodily substance. The prosecution does not need to prove impairment. The number alone is sufficient.
That sounds simple for the state. But the evidence they rely on to prove that number is far more vulnerable than most defendants realize.
Evidence the State Relies On
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Breathalyzer results (evidentiary test): The primary evidence in most per se DUI cases. Illinois uses devices like the Draeger Alcotest. Under 20 Ill. Adm. Code 1286.200, these machines must be calibrated at least every 62 days. The operator must be certified. A 20-minute continuous observation period must be completed before testing. Failure at any step can make the result inadmissible.
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Blood test results: Used when breath testing is unavailable or when the driver is hospitalized. Blood draws require proper chain of custody, correct storage temperature, and qualified phlebotomy. Contamination, fermentation, and lab error have all been successfully challenged in DuPage County.
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Officer testimony: Even in per se cases, officers will testify about the reason for the stop, observations at the scene (odor of alcohol, bloodshot eyes, slurred speech), and your performance on field sobriety tests. This testimony supports the BAC evidence but is subjective and challengeable.
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Dash cam and body cam footage: Video evidence can work both ways. It may show driving behavior consistent with impairment, but it can also reveal an improper traffic stop, a well-performing driver, or inconsistencies between the officer's written report and what actually happened on camera.
Defense Strategies
How We Fight
a Per Se DUI Charge
A BAC number over 0.08% does not guarantee a conviction. The number is only as reliable as the machine, the operator, and the procedures used to produce it. Here are the defense strategies our attorneys use most effectively in (a)(1) cases.
The Fourth Amendment requires police to have reasonable suspicion before pulling you over. If the stop was based on a hunch, a minor equipment violation with no actual observation, or happened at a checkpoint that was not conducted according to Illinois guidelines, all evidence collected after the stop can be suppressed. This includes the breathalyzer results. A successful suppression motion often leads to full dismissal.
We subpoena the calibration and maintenance records for the specific device used in your test. Under Illinois administrative code, breath testing instruments must be calibrated at least every 62 days. The machine is only certified as accurate within a margin of plus or minus 0.01. If your BAC was 0.09% and the machine was overdue for calibration, the true reading may have been below the legal limit. One missed maintenance interval can render the entire result inadmissible.
Illinois law requires the officer to continuously observe you for 20 minutes before administering the evidentiary breath test. During this period, you cannot burp, vomit, eat, drink, or put anything in your mouth, as any of these can contaminate the breath sample and produce a falsely high reading. If the officer was distracted, stepped away, or failed to document the observation, the test result is challengeable.
The law requires your BAC to be 0.08% at the time of driving, not at the time of testing. Breath tests typically happen 45 to 90 minutes after the traffic stop. If you had recently consumed alcohol, your BAC was still rising during that window. It is possible your BAC was below 0.08% when you were actually behind the wheel and only exceeded the limit later at the station. An expert toxicologist can establish this timeline.
Certain medical conditions can produce falsely elevated BAC readings. Acid reflux (GERD), diabetes, and certain ketogenic diets can cause mouth alcohol or acetone that breathalyzers misread as ethanol. If you have a documented medical condition that could affect the test, we can present expert testimony to undermine the reliability of the result.
When the evidence is strong and suppression is not viable, court supervision is the best available outcome for a first offense. It avoids a formal conviction on your record if you complete all conditions. You can only receive court supervision for DUI once in your lifetime in Illinois. Making sure the terms are favorable requires an experienced negotiator who knows DuPage County judges and prosecutors.
Legal Process
What Happens After
a Per Se DUI Arrest
A DUI arrest in DuPage County triggers two separate legal proceedings: the criminal case and the administrative Statutory Summary Suspension of your license. Both have hard deadlines. Missing them is costly.
You are arrested and taken to the station for an evidentiary breath test. If you blow 0.08% or higher, the officer issues a Notice of Statutory Summary Suspension. This notice serves as your temporary driving permit for 45 days. You have 90 days to petition the court to rescind the suspension.
We file a petition to rescind the summary suspension and immediately begin requesting dash cam footage, breathalyzer calibration records, operator certifications, and the full police report. Video evidence is often destroyed after 30 days if not formally requested. Speed matters here.
Unless we successfully rescind the suspension, your driving privileges are suspended on day 46. First-time offenders who failed the test face a 6-month suspension. A Monitoring Device Driving Permit (MDDP) with a BAIID ignition interlock device allows most first-time offenders to keep driving with restrictions.
You are formally charged and enter a not guilty plea. Pretrial hearings follow. This phase includes motions to suppress evidence, including breathalyzer results, field sobriety tests, and video footage. This is where most per se DUI cases are won or lost.
Most DuPage County per se DUI cases resolve within 6 to 12 months. Possible outcomes include full dismissal (if evidence is suppressed), court supervision (no conviction on record), reduced charge, or trial. We prepare every case as if it is going to a jury.
FAQ
DUI Over 0.08 BAC:
Common Questions
Yes. Under 625 ILCS 5/11-501(a)(1), the prosecution does not need to prove impairment. A BAC of 0.08% or higher is enough on its own. Even if you were driving safely, obeying all traffic laws, and performing well on field sobriety tests, the BAC number alone satisfies the elements of the offense. However, video showing normal driving can still be valuable in negotiations or at trial, especially when paired with challenges to the test accuracy.
Borderline cases are some of the most defensible. Illinois breath testing machines are only certified as accurate within a margin of plus or minus 0.01. That means a reading of 0.08% could reflect a true BAC as low as 0.07%. Combined with the rising BAC defense and any calibration irregularities, borderline results are very vulnerable to challenge.
For a standard first offense with no aggravating factors, jail time is possible but not mandatory. Most first-time offenders who receive court supervision serve no jail time. However, if your BAC was 0.16% or higher, a minor was in the vehicle, or an accident occurred, you may face mandatory sentencing. See our full penalty guide.
The (a)(1) charge is the "per se" DUI. It requires a BAC of 0.08% or higher from a chemical test. No proof of impairment is needed. The (a)(2) charge is "under the influence" DUI. It requires the prosecution to prove you were actually impaired by alcohol, typically through officer testimony and field sobriety test results. Most DUI arrests result in both charges being filed together. If we suppress the breathalyzer, the (a)(1) count falls, and the prosecution must rely entirely on the weaker (a)(2) count.
The total cost including fines, court costs, evaluation fees, BAIID device rental, attorney fees, increased insurance premiums, and lost wages is commonly estimated at $16,000 to $25,000 over several years. And that is before any long-term career impact from a permanent criminal record. Read our full DUI cost breakdown.
Expungement
Can a DUI Over 0.08 BAC
Be Expunged in Illinois?
Cannot Be Expunged
Under Illinois law, DUI convictions are explicitly excluded from expungement and sealing. There is no waiting period. There is no petition process. A conviction under 625 ILCS 5/11-501(a)(1) stays on your record permanently. This is one of the most serious consequences of a DUI and a primary reason to fight the charge aggressively from the start.
There is one important exception. If you receive court supervision and complete all conditions, supervision is not a conviction. The supervision record may be eligible for expungement after a waiting period. An arrest that results in no conviction may also be expungeable. This is another reason court supervision, or better yet full dismissal, is the outcome worth fighting for.