Indiana Cannabis DUI & the Per Se Metabolite Rule

Last verified: April 2026

The Per Se Metabolite Rule: IC 9-30-5

Most states distinguish between active THC (delta-9-THC) and the inactive carboxy-THC metabolite (THC-COOH) that the body produces as it processes cannabis. Active THC indicates recent use and can correlate with impairment; carboxy-THC is what shows up on a urine drug screen and persists for days to weeks after exposure, depending on body fat percentage and frequency of use.

Indiana’s OWI statute, IC 9-30-5-1(c), does not draw that line. Operating a vehicle with any Schedule I or II controlled-substance metabolite in the body is per se illegal, with no impairment showing required. THC and its metabolites are listed in the chemical-test schedule, and the inactive carboxy metabolite is sufficient to support a conviction.

A person who operates a vehicle with a controlled substance listed in schedule I or II of IC 35-48-2 or its metabolite in the person's blood commits a Class C misdemeanor.

Indiana Code § 9-30-5-1(c)

The 2020-21 Affirmative Defense

The legislature’s only meaningful adjustment came in P.L. 142-2020 and P.L. 49-2021, which added a narrow marijuana-metabolite affirmative defense codified at IC 9-30-5-1(d). A driver may avoid conviction by proving, by a preponderance of the evidence, that:

• The substance was consumed in accordance with the laws of another state (e.g., a regulated Michigan or Illinois dispensary purchase consumed in that state); and
• The driver was not impaired at the time of operation.

The defense is the affirmative kind — it must be raised and proved by the defense, not disproved by the state. It does not apply to drivers consuming cannabis in violation of another state’s law (an under-21 Michigan adult-use buyer, for example, is not protected). And it does nothing for drivers who consumed legally elsewhere but were genuinely impaired at the wheel.

Sentencing Tiers Under IC 9-30-5

Conviction of a metabolite-only Class C misdemeanor still triggers a mandatory administrative license suspension and a 90-day to one-year court-ordered suspension under IC 9-30-5-10.

Implied Consent and Refusal

IC 9-30-6 treats operating a vehicle as consent to chemical testing on probable cause. Refusal triggers a one-year automatic license suspension under IC 9-30-6-7(b) and IC 9-30-6-9, separate from any criminal disposition. The chemical test must be administered within three hours of probable cause arising. Indiana is one of nine states that imposes criminal penalties for refusal in some circumstances; in most cannabis-only stops the consequence is the administrative suspension rather than a separate criminal count.

Drug Recognition Experts (DREs)

The Indiana State Police DRE program trains officers in a 12-step impairment evaluation modeled on the IACP/NHTSA national protocol. DRE testimony — pulse, eye tracking, divided-attention performance, body temperature, muscle tone — is admissible in Indiana courts but not dispositive. Most metabolite-positive cases rest on the chemical test alone; DRE evaluations carry more weight in active-impairment cases where a driver’s behavior at the stop is the central evidence.

Probable Cause from the Smell of Marijuana

Indiana courts continue to permit warrantless searches of vehicles based on an officer’s detection of the smell of marijuana — the “plain smell” doctrine. Since 2018, when SEA 52 legalized hemp under 0.3% delta-9 THC, the same olfactory profile attaches to lawful smokable hemp products available in border states and to lawful Indiana hemp flower (during the windows when the SEA 516 ban was unenforceable). Smokable hemp and marijuana are functionally indistinguishable to the human nose and indistinguishable to the naked eye.

Suppression motions challenging the marijuana-odor predicate have proliferated since 2019, particularly in Marion, Monroe, and St. Joseph counties. The Indiana Supreme Court has not categorically rejected the doctrine. In Bunnell v. State (2020) and subsequent decisions, the Court has narrowed but not eliminated odor-alone probable cause, generally requiring corroborating indicia (visible flower, paraphernalia, inconsistent statements). Defense practice in this area is among the most active in Indiana criminal law.

Cross-Border Risk: Days After You Drove Home

The combination of per se metabolite liability and 30-day metabolite persistence creates real exposure for Hoosiers who legally consume cannabis on a Niles, Michigan or Danville, Illinois trip and then drive in Indiana days or weeks later. The 2020-21 affirmative defense provides a path, but it requires affirmative proof, expert testimony, and counsel willing to litigate the issue. ISP Superintendent Doug Carter has publicly stated his agency has not seen a metabolite-DUI surge attributable to neighbor-state legalization, and Indiana does not publicly aggregate metabolite-only conviction figures distinct from impairment OWIs — but the statutory structure remains.

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