IL SB3409

Clarifies that the illegal THC threshold for driving is "free tetrahydrocannabinol" (unchanged parent delta-9-THC) of 5 nanograms or more per milliliter in whole blood or 10 nanograms or more per milliliter in other bodily substances, measured within 2 hours of driving.

Defines "free tetrahydrocannabinol concentration" as the amount of unchanged, parent delta-9-tetrahydrocannabinol detected in a blood or bodily fluid sample, distinguishing it from metabolites.

Exempts qualifying medical cannabis patients with valid registry cards from the THC limit violation, unless impaired by cannabis use.

Allows law enforcement to use validated roadside chemical tests and standardized field sobriety tests approved by the National Highway Traffic Safety Administration when investigating cannabis-impaired driving.

Makes technical amendments to Section 11-501.2 to align testing standards and presumptions with the new free THC concentration definition.