Is there a legal THC limit in Illinois?

Illinois uses specific THC thresholds for certain inferences, but the key issue remains proof of impairment at the time of driving.

Do metabolites alone prove DUI?

Inactive metabolites are not the same as active impairment; interpretation depends on the test and context.

What about medical cannabis card holders?

Having a card does not permit impaired driving; evidentiary and impairment standards still apply.

Are field sobriety tests valid for cannabis?

Standardized field sobriety tests were developed for alcohol; their application to cannabis is often contested and must be evaluated with the video and instructions given.

Illinois DUI

Cannabis / Marijuana DUI

THC thresholds, impairment proof, and lab challenges in Cook, DuPage, Will, Kane, and Lake.

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What the State Must Prove

Driving + Impairment

Cases hinge on proof of impairment at the time of driving—not mere prior use. Video, dispatch logs, and witness accounts matter.

Testing & Collection

Timing of blood/urine draws, chain-of-custody, instrument validation, and sample storage conditions can affect accuracy.

DRE & Observations

Drug Recognition Expert opinions and officer narratives are compared against body-cam, medical records, and science.

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Common Challenges in Cannabis DUI

Delay between driving and sample collection
Metabolite vs. active THC interpretation
Prescription/medical documents and tolerance
Field tests not validated for cannabis impairment
Collection kits, lab protocols, and reporting variance

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Courts We Serve

Cook • DuPage • Will • Kane • Lake

Cook County

Chicago (Daley Center)
Skokie
Rolling Meadows
Maywood
Bridgeview
Markham

DuPage County

Wheaton (Main Courthouse)
Glendale Heights (Branch)

Will County

Joliet (Main Courthouse)
Bolingbrook (Branch)
Plainfield (Branch)
Frankfort (Branch)

Kane County

Geneva (Kane County Courthouse)
St. Charles (Judicial Center)
Aurora (Branch)
Elgin (Branch)

Lake County

Waukegan (Main)
Park City (Branch)
Round Lake (Branch)
Mundelein (Branch)

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Cannabis DUI FAQs

Is a positive THC test enough?

Context, timing, and impairment evidence matter. Metabolites alone may not prove impairment.

Can I drive with a medical card?

Driving while impaired is still prohibited; documentation and science are key.

What samples are used—blood or urine?

Both appear in cases. Collection timing, storage, and lab protocols affect reliability and interpretation.

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