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. In Corry's view, "the permissible inference is a small step in the right direction. But the way I couched it last year was, if the bill can't be voted down, this is a fallback position. If it's a choice between per se and permissible inference and voting the bill down is not an option, then permissible inference would be better than per se. But I still think the current law is more than adequate, and probably more harsh."

As Corry points out, driving under the influence of marijuana is illegal right now, and would continue to be if the bill falls short a third time. "Prosecutors charge DUID [driving under the influence of drugs] quite frequently, and win much more often than they lose" -- around 90 percent of the time, according to an estimate offered by the Medical Marijuana Industry Group last year. "so the current law is already geared to driving people toward convictions and is fine to protect public safety."

Why, then, is there such a push for a THC driving standard? Right now, Corry explains, "the defendant is innocent until proven guilty." But under a permissible defense, "it would basically be guilty until proven innocent. A defendant who walks into court is assumed to be guilty" if he tested at five nanograms or above, "and he has to prove a negative -- that he wasn't intoxicated. And that's very hard to do."

This isn't the only problem with the legislation, in Corry's view. "The main problem is that the five nanogram number is a random number, a political number. There's no science that supports the number five, no study that says you're okay at four and not okay at six. The number was pulled out of a hat and the science isn't there. What that will mean is innocent people will be convicted. It will be a luck factor based on whether they can persuade a jury they're inoocent, because they walk in presumed guilty."

Do studies support his position. "They do," he says. "Science says marijuana effects everybody differently, and there are extreme differences between one person and another" -- especially medical marijuana patients who use so frequently that inactive THC lingers in their system.

Even so, the momentum appears to be with the THC driving bill this time around. Yet Corry isn't ready to surrender.

"It sure seems like God does not want this bill to pass," he says. "They've tried so many times before, and was supposedly a foregone conclusion that it would pass last year. But thanks to a combination of luck and sustained advocacy, it's been defeated multiple times.

"Maybe everything will come together again and this bill will die yet again. I hope so."

Look below to read the draft language for the current bill, followed by Corry's February 2012 letter.

More from our Marijuana archive: "THC driving bill: Marijuana lawyer Rob Corry suggests a compromise."

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