Anywhere from a few dozen to more than 10,000 people could be eligible to have their old marijuana convictions overturned as the result of a landmark Colorado Court of Appeals ruling that applied marijuana legalization retroactively.

Colorado defense attorneys are poring through previous marijuana cases, looking for former clients who might be eligible for such relief, but much depends on how subsequent courts apply this month’s ruling. On the surface, the ruling appears to have little reach, but attorneys say it is possible courts could follow the reasoning of the ruling to overturn every marijuana case in the state in which an adult was convicted of a crime that stopped being illegal when the state’s marijuana-legalization law went into effect in late 2012.

“I think there are thousands of people who could potentially have their convictions overturned,” said Sean McAllister, an attorney who specializes in marijuana cases and who said he is already working with several clients to see if their previous convictions could be tossed.

But, in order for that to be true, Colorado courts will have to adopt an expansive reading of the ruling — a scenario prosecutors see as unlikely.

“I think that’s a tortured application of the (appeals court’s) holding,” said Tom Raynes, executive director of the Colorado District Attorneys’ Council.

The appeals court’s decision, released earlier this month, overturned two marijuana convictions for a woman found guilty in 2011 of things that are no longer illegal under state law as a result of Amendment 64. The amendment, which went into effect on Dec. 10, 2012, makes it legal for people 21 and older to possess up to an ounce of marijuana or marijuana concentrate and grow up to six marijuana plants.

In the key passage from its ruling, the appeals court found that “a defendant is entitled to the benefits of amendatory legislation that mitigates the penalties for crimes when he files a motion for postconviction relief.”

That means anyone who currently has a pending appeal for a pre-Amendment 64 conviction or anyone who is still eligible to appeal such a conviction has a good chance of seeing it overturned, McAllister said. The catch, though, is that the window to appeal has closed in most cases where people were convicted of crimes that are now legal.

From January through November 2012, for instance, about 4,800 people over 21 years old were charged with petty possession of less than 2 ounces of marijuana, according to a Denver Post analysis of court data for every county in Colorado except Denver. Only about 900 of those charges resulted in some type of finding of guilt — most were dismissed. But for petty convictions, state law allows only a six-month appeal window, which is long closed.

Misdemeanors have an 18-month window, meaning there is a chance people convicted before Amendment 64 of possessing less than an ounce of marijuana concentrate or growing up to six plants could still be able to appeal. But The Post’s analysis found fewer than 100 such cases that could potentially fit within the right time frame — and only a handful where the marijuana charge was the only charge.

Not looking for cases

A spokesman for the Colorado Judicial Branch said courts have not tried to identify how many pending appeals or so-far unappealed cases could be eligible for retroactive relief. And the Colorado attorney general’s office plans to appeal to the state Supreme Court, meaning the Court of Appeals’ ruling could be overturned.

Defense attorney Jeff Gard said there is one way tens of thousands of people could see their marijuana convictions tossed — even if they occurred long ago. State law allows people to appeal their convictions at any time if they can show “justifiable excuse or excusable neglect.”

“That’s exactly what we have here,” Gard said. “Anybody who was walking down the street didn’t know they had the opportunity to appeal until this ruling came out.”

Attorney Patrick Mulligan, who specializes in appellate law, agreed that defendants could try such an argument. But he said courts usually set the bar extremely high for appeals filed outside the statute of limitations.

“The case law has made it very, very difficult for defendants to fit within the statutory definition of ‘justifiable excuse’ or ‘excusable neglect,’ ” Mulligan said.

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/john_ingold

The ruling: The Colorado Court of Appeals held that those charged with certain marijuana crimes before the Amendment 64 legalization of pot may be able to appeal those penalties.

The impact: Defense lawyers say more than 10,000 people may be eligible to have their marijuana convictions overturned, but prosecutors say that requires a broader interpretation.