As our Melanie Asmar reported, the Amendment 64 Task Force backed passage of a marijuana DUI bill during a meeting earlier this month. The current legislation tweaks a version that's failed each of the past two years, incorporating a suggestion that marijuana attorney Rob Corry floated last year. Does that mean Corry supports the current measure? In a word, no.

Some background: As we've reported, Representative Claire Levy sponsored a bill in 2011 that would have established THC intoxication at five nanograms per milliliter of blood. Levy later decided this standard was too strict, and suggested that an 8 nanogram limit be substituted, but she didn't win the argument. The five nanogram version subsequently passed the Colorado House.

But following a report that Westword medical marijuana critic William Breathes's blood had tested at nearly three times the legal amount while sober, the aforementioned senate judiciary committee shelved the proposal pending future study, and an attempt to resurrect it again in May failed.

Months later, a divided DUID-marijuana working group failed to come to a consensus, with half the members in favor of a per se limit -- meaning that a test registering five nanograms or more would be seen as irrefutable proof of intoxication -- and the other half maintaining that unlike alcohol, THC tends to linger in users for longer periods of time, making it next to impossible to determine actual impairment via a blood test, at least under currently available technology.

Nonetheless, Senator Steve King introduced the bill again in 2012, and after being revived for a special session, it seemed a lock to pass. Instead, it fell one vote short, because Senator Nancy Spence was in California for her grandson's birthday.

Cut to this past December, when another pair of legislators took the bill out of mothballs again, but this time with a difference. Rather than a per se limit, a so-called "permissible inference" defense would be allowed. As William Breathes wrote, a test above five nanograms wouldn't automatically infer guilt: "If...other evidence indicated he was not impaired, the jury could find in favor of the defendant."

In February 2012, Corry made a pitch for this same approach using an equivalent term -- "rebuttable presumption." In an open letter the legislators, he wrote:

If the bill cannot be voted down at this stage, at the very least, there should be an amendment that makes the five nanogram level a rebuttable presumption, and gives drivers an affirmative defense to demonstrate to a jury or judge that they were not impaired.

Nonetheless, Corry says, "I don't support the current bill."

Why not? "If the per se bill was 100 percent bad," he allows, "this one is 95 percent bad."

Continue to read more about the latest THC driving bill.