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DENVER — Police say Richard Kirk smoked and ate marijuana products just hours before shooting his wife to death in their home last week.

And that could be a key part of his defense.

He’s charged with first degree murder in the death of his wife Kristine.

Some say he will never be convicted of first degree murder.

Legal experts say it’s different than alcohol, where the effects are predictable. Legal marijuana and edible marijuana in particular is so new, it could be argued Kirk did not realize how it would affect him.

Police say Kirk admits he shot and killed his wife in the home on South St. Paul Street near East Evans Avenue while she was on the phone with 911.

“I don’t see a first degree murder conviction,” says legal analyst Dan Recht.

One of the first things Kristine Kirk told 911 was that her husband had been using marijuana.

Recht says that will be one of the first things his defense attorneys argue. “The defense will bring up intoxication by high concentration of marijuana. With absolute certainty you will see it as part of their defense.”

According to the incident detail report FOX31 Denver obtained which details the 911 call, Kristine Kirk told the operator her husband had taken marijuana and was hallucinating.

Other police documents reveal the 911 call taker heard Kirk in the background talking about taking marijuana candy.

Police found he bought edible marijuana called Karma Kandy Orange Ginger less than three hours before the shooting.

“This is really uncharted territory,” Recht says.

He also says while being drunk typically isn’t a defense, the unknowns about edible marijuana and its effects on people will be used in this case. “The defense will argue strongly that this is an involuntary intoxication in the sense that he didn’t know it would produce this kind of effect on his mental state.”

The reason this is so important is the sentencing. A first degree murder conviction could mean life in prison but if Kirk is convicted on a lesser charge such as manslaughter, he might only get probation and not serve any prison time at all.