There are already plans to reintroduce a limit during next year's session, but critics are suggesting they'll once again keep a close eye on anything that would place a hard limit on drivers.
"While I agree people shouldn't drive impaired, I also don't think innocent people should be convicted," attorney Sean McAllister said. "The science still isn't clear on this issue."
Currently, it's primarily the job of the responding police officer to determine if a driver is too impaired to drive as a result of smoking marijuana, as there is no agreed-upon number as to when impairment actually occurs. With alcohol, the standard for DUI in Colorado is a 0.08 percent blood alcohol content.
During the past two legislative sessions, there have been efforts to set Colorado's marijuana standard at 5 nanograms of THC per milliliter of blood (THC is the primary psychoactive ingredient of marijuana).
Those efforts have failed for a variety of reasons, but next year's renewed push will carry with it the fervor surrounding the passage of Amendment 64. Earlier this month, by a 55-45 margin, voters in Colorado joined with voters in Washington state in becoming the first states to legalize the recreational possession and sale of marijuana.
"I do have concerns as to how this is going to impact driving," Adams County District Attorney Don Quick said. "I think if you are going to err on the side of caution, you ought to err on the side of the people who aren't getting stoned."
Quick supports a 5 nanogram limit in part because it would set a uniform standard that would be recognizable by prosecutors and jurors alike.
"I think it would be a deterrence for people," Quick said.
Part of the problem lies in the different opinions as to how long THC can stay in the system after smoking marijuana.
The Colorado District Attorney's Council suggests, "Even in chronic users, THC levels normally drop below 5ng/ml within three hours after use."
It also says a person with a 5 ng/ml is 6.6 times more likely to cause a crash than someone with no THC in his or her system.
McAllister said he is currently working a case where a driver with 6 ng/ml THC level was flagged for DUI. He said the driver smoked the previous day and was not impaired to drive at the time.
"If we pass a hard-line standard we're not going to go to trial on these cases any more. It's going to change the standards where the prosecution has the presumption of guilt rather than the defendant having the presumption of innocence," he said.
Washington passed a per se 5 nanogram limit when voters passed their legalization question earlier this month.
(KUSA-TV © 2012 Multimedia Holdings Corporation)