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Idaho Cannabis DUI — Per-Se Zero Tolerance

Idaho applies per-se zero-tolerance for marijuana metabolites in some prosecutions. Any detectable THC or carboxy-THC in blood can support a DUI conviction even days after consumption.

Last verified: April 2026

The Statute — §18-8004

§18-8004, the DUI statute, criminalizes operating a vehicle under the influence of any intoxicating substance. Idaho applies a per-se zero-tolerance standard for marijuana metabolites in some prosecutions: any detectable THC or carboxy-THC in blood can support a DUI conviction even days after consumption.

Why This Matters for Cross-Border Travelers

Legal Use in Oregon Yesterday Can Be Idaho DUI Today

Cannabis metabolites (carboxy-THC, the inactive THC breakdown product) can remain in blood and urine for days to weeks after consumption — long after any actual impairment has dissipated. Idaho's per-se zero-tolerance standard treats any detectable metabolite as a DUI predicate. A weekend trip to Oregon for legal cannabis can produce an Idaho DUI on the drive home or even the next day.

Penalties

  • 1st offense — misdemeanor; up to 6 months jail, $1,000 fine, 90-day to 1-year license suspension, mandatory drug evaluation, possible ignition interlock.
  • 2nd offense (within 5 years) — misdemeanor; up to 1 year, longer license suspension, mandatory ignition interlock.
  • 3rd offense (within 10 years) — felony; 30 days to 5 years, $5,000.
  • Excessive DUI (BAC ≥ 0.20% or significant THC) — enhanced penalties.

Commercial Drivers — Federal DOT

Commercial drivers (CDL) are subject to federal DOT rules under 49 CFR Part 40 and lose their licenses for any positive cannabis test regardless of state of consumption. The federal Drug and Alcohol Clearinghouse maintains the record visible to all CDL employers.

Implied Consent

Idaho's implied-consent law treats operating a motor vehicle as consent to chemical testing when an officer has reasonable grounds. Refusal results in automatic license suspension separate from any criminal conviction.

Defense Realities

  • Chain-of-custody challenges on blood and urine samples.
  • Per-se threshold disputes — Idaho law is somewhat less clear than statutory zero-tolerance jurisdictions.
  • SFST and Drug Recognition Expert reliability — DRE certification and field-condition variables.
  • Carboxy-THC vs active THC — defense expert testimony that metabolites do not reflect impairment.

Reading the Statute

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