'Marijuana sweets made me kill my wife.'

A US man who claimed eating marijuana-infused sweets led him to kill his wife has been sentenced to 30 years in prison.

Richard Kirk, 50, was charged in the April 2014 shooting of Kristine Kirk at the couple’s home in Denver, Colorado.

Moments before he shot her in the head, Kristine Kirk said in an emergency call her husband was hallucinating and was getting a gun after eating pot sweets.

Kirk initially pleaded not guilty to first-degree murder but later changed his plea to not guilty by reason of insanity, claiming he was intoxicated with THC, marijuana’s psychoactive ingredient.

He pleaded guilty to second-degree murder in a deal with prosecutors in February, avoiding a potential life sentence.

Prosecutor Helen Morgan said after Friday’s hearing that Kirk’s use of marijuana played a role in deciding to broker a plea deal.

Kirk’s lawyers sought lenience on the grounds he had consumed THC to relieve back pain and it had severely impaired his judgment.

They also argued he suffered “involuntary intoxication” because he did not know he was at high risk for marijuana psychosis due to schizophrenia in his extended family.

Denver District Judge Martin Egelhoff did not address that argument during sentencing.

Investigators say the couple had escalating marital and financial problems, and Kristine Kirk had told a friend she was afraid of her husband because they had been fighting so much – a conclusion disputed by the defence.

Kirk said in court his wife would still be alive if he had not eaten marijuana sweets.

“I had no idea how it would affect me. … I’m so sorry that I became the monster that I was supposed to protect them from,” he said of his family.