Washington’s 5 ng/mL THC Limit Was Never About Science. SB 6012 Would Finally Admit That.

Washington’s 5 ng/mL THC Limit Was Never About Science. SB 6012 Would Finally Admit That. A the full legislative tracker moving through Olympia would replace the state’s blunt-instrument cannabis DUI standard with actual impairment testing. The vote is April 14.

When Washington voters passed I-502 in 2012 and legalized recreational cannabis, lawmakers needed a number. Something clean, defensible, a threshold that could stand up in court the way 0.08 BAC did for alcohol. They landed on 5 nanograms of THC per milliliter of blood.

The problem, which scientists were saying out loud at the time, is that the number doesn’t mean what people think it means. SB 6012 is Olympia’s attempt to finally deal with that.

The bill passed the Senate Law and Justice Committee 7-2 on March 8. A full chamber vote is scheduled for April 14.

What This Bill Actually Does

SB 6012 repeals Washington’s per se cannabis DUI limit — the automatic presumption of impairment triggered when a blood draw shows 5 ng/mL of THC or above — and replaces it with an impairment-based standard assessed through standardized field sobriety evaluation.

Under the current system, if you’re pulled over and blood is drawn, a THC reading at or above 5 ng/mL is legally equivalent to being drunk. No further evidence of impairment is required.

Under SB 6012, impairment would have to be demonstrated — through the same officer-administered sobriety tests already used for alcohol, as well as Drug Recognition Expert evaluation where applicable. The blood draw doesn’t disappear from the evidence toolkit; it loses its status as automatic proof.

If the bill passes the full legislature and is signed into law, it takes effect January 1, 2027. Law enforcement agencies statewide would be required to complete retraining on the updated impairment assessment protocol before that date.

Who It Affects

Washington has approximately 1.2 million adults who report using cannabis in the past month, according to state survey data. Of that group, a significant portion — regular users, daily medical patients, and older consumers who metabolize THC differently — can carry blood THC levels above 5 ng/mL days after their last use, long after any actual impairment has passed.

That’s the core problem. THC is fat-soluble. It doesn’t clear the blood on any predictable schedule. A person who smoked Friday night and drives to work Monday morning can still test above 5 ng/mL. They are not high. They are, under current Washington law, presumptively impaired.

For medical cannabis patients — those treating chronic pain, epilepsy, PTSD — the per se standard has functioned as a persistent DUI threat even during periods of full sobriety. A sober drive to a doctor’s appointment could still result in a charge.

SB 6012 would change that. The standard becomes: can an officer demonstrate, through observed behavior and field evaluation, that this person cannot safely operate a vehicle right now?

The Direction

This is a reform that expands procedural fairness for cannabis users without removing the state’s ability to prosecute impaired driving.

That distinction matters. Opponents of the bill — and there are some, including a minority faction on the Law and Justice Committee — will frame this as weakening impaired driving enforcement. That framing is worth examining. Field sobriety tests are already the primary tool for alcohol impairment detection above the 0.08 threshold. DUI law for alcohol doesn’t automatically trigger on a single blood marker divorced from behavior. Cannabis has been held to a stricter standard, and SB 6012 asks why.

Washington is not the first state to revisit this. Colorado, which has used a similar 5 ng/mL limit since its own legalization, has seen sustained legislative pressure to move toward impairment-based standards. Colorado’s standard is technically rebuttable in court, but the presumption still weighs heavily in prosecutions. Oregon, which operates under a different DUI framework, has never used a per se THC limit and relies on observed impairment and DRE evaluation. So far, Oregon’s data has not shown worse impaired driving outcomes as a result.

What Happens Next

– April 14, 2026: Full Senate floor vote on SB 6012 – If passed: Moves to the House; must pass both chambers before the legislative session ends – If signed into law: Takes effect January 1, 2027 – Before January 2027: Statewide officer retraining on updated impairment protocols required

The bill’s 7-2 committee vote signals broad support in the Senate. The House represents the next hurdle. Law enforcement associations have historically opposed any weakening of per se standards — their argument is procedural certainty in court — so House testimony will be worth watching.

Who’s Behind This

The 7-2 committee vote suggests this is not a narrowly partisan bill. Cannabis-adjacent reform in Washington has generally attracted bipartisan support since I-502 passed with 56 percent of the vote in 2012. The two dissenting votes on the Law and Justice Committee align with the law enforcement advocacy position: that a per se standard, however imperfect, provides clean prosecutorial footing.

That’s an understandable concern for prosecutors. It’s less defensible as science.

The strongest opposition to SB 6012 will likely come not from anti-cannabis hardliners but from DUI defense and prosecution attorneys who have spent fourteen years building practice around the existing standard. Disrupting legal precedent has costs, and those costs are real. The argument from reform advocates is that the current standard has already been exacting costs — just on cannabis users who tested positive while sober.

The cannabis industry itself has a quieter stake in this. Dispensaries near Washington’s major highways field questions about the 5 ng/mL limit constantly. Medical patients who drive are the ones most directly chilled by the existing law.

CannabisInquirer will update this article with confirmed bill sponsors and primary opponents as the April 14 vote approaches.

The Bottom Line

Washington set a cannabis DUI standard in 2012 that the science never supported, because legalization needed a number and 5 ng/mL sounded like one. SB 6012 doesn’t go soft on impaired driving — it asks that “impaired” actually mean something. If it passes the full legislature, Washington becomes the most significant state to formally abandon the per se THC standard, and every other legal state with a similar limit will be watching.

The vote is April 14. Pay attention.

Sources: Washington State Legislature (SB 6012 — passed Senate Law & Justice Committee 7-2, March 8, 2026); NORML; state cannabis use survey data (WA Dept. of Health). Bill source: app.leg.wa.gov.

Jo Tanaka covers the West and Pacific for CannabisInquirer.com. Portland-based. Former dispensary consultant. Reach her at [editorial contact].