Yesterday a Colorado Senate committee killed a bill that would have allowed juries to convict people of driving under the influence of drugs based on nothing more than a test indicating a THC concentration of five nanograms per milliliter of blood. That cutoff has no real scientific basis, and experiments indicate that many pot smokers can drive competently at THC levels far above it. Bills aimed at establishing a per se DUID standard of five nanograms have failed repeatedly in Colorado because of concerns that it is not a good indicator of impairment. But after voters approved Amendment 64 last November, supporters of a new DUID rule tried again, arguing that marijuana legalization would lead to increased consumption, magnifying the danger posed by stoned drivers.

This time around, backers of H.B. 13-1114 offered a compromise: Instead of being automatically guilty of DUID at five nangograms (which is now the rule in Washington under I-502, that state's marijuana legalization initiative), drivers who tested at or above that level could present evidence that they were not in fact impaired. But that approach still shifted the burden of proof from prosecutors, who under current law have to present evidence of impairment, to defendants, who would have to rebut what in practice might prove to be a powerful presumption of guilt. With a "permissible inference" of DUID at five nanograms, says Denver attorney Rob Corry, "A person coming into court is guilty until proven innocent….If you put a number on it, juries are going to latch onto that five-nanogram number, whether it's a permissible inference or a per se [standard], and the effect will be that innocent people are convicted, whether or not they're impaired."

H.B. 13-1114, which was endorsed by the Amendment 64 Implementation Task Force (a panel appointed by Gov. John Hickenlooper to advise the state legislature on how to regulate marijuana), received final approval from the state House of Representatives on April 5. But on Monday the Senate Judiciary Committee, by a 3-to-2 vote, decided to indefinitely postpone consideration of the bill with just two weeks to go in the current legislative session. "What is the problem we're trying to solve?" asked Sen. Jessie Ulibarri (D-Commerce City), vice chairman of the committee. "I take it very seriously for people to drive impaired," said Sen. Kevin Lundberg (R-Berthoud), another committee member. "I also take it very seriously for the government to prosecute people who aren't impaired."