DENVER (CBS4) – A man accused of killing his wife while high on a marijuana edible pleaded not guilty on Friday.

The murder happened inside the couple’s home in Denver’s Observatory Park neighborhood last year. Richard Kirk’s wife Kristine was on the phone with 911 for more 12 minutes when the fatal shot was fired.

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Richard Kirk (credit: Denver Police Department)

Richard Kirk (credit: Denver Police Department)

There has been no denying that Richard Kirk fired the shot that killed his wife, but he had eaten part of a marijuana laced cookie, and his lawyer may very well argue he was not responsible for his actions.

Just before she was shot to death, Kristine Kirk told a 911 operator her husband had taken a marijuana edible and possibly back pain medicine and was hallucinating.

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Richard Kirk’s brother was among those in court as the not guilty plea was entered, setting the stage for a possible marijuana related defense. CBS4 legal analyst Karen Steinhauser says it would involve use of a Colorado law addressing the impact from a use of a substance.

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“But the substances produce an effect that was not anticipated; then you have an involuntary intoxication, which is a complete defense to a charge,” Steinhauser said.

At the Kirk home Kristine Kirk told the operator her husband at first wanted her to shoot him. Then he went to the safe for the weapon.

(credit: Family of Kris Kirk)

(credit: Family of Kris Kirk)

Prosecutors have produced testimony that the Kirks were having marital and financial problems.

“But when you have evidence of a possible motive, it’s going to be a lot more difficult for the jury to accept that this truly was an involuntary intoxication situation,” Steinhauser said.

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A marijuana defense was recently used in Boston related to the Boston Marathon bombing. A friend of the accused bomber now on trial claimed to be “high out of his mind” when he spoke to investigators. He was promptly convicted of helping in a cover up.