COEUR d’ALENE — Defense attorneys are asking the court to dismiss murder charges against a Post Falls man accused of killing his girlfriend by allegedly injecting her with heroin.

In motions filed in First District Court, Kootenai County Public Defender Anne Taylor accused prosecutors of failing to provide exculpatory evidence to the grand jury that indicted Ryan A. Forbes for second-degree murder.

In an eight-page motion considered by District Judge Lansing Haynes, Taylor said prosecutors painted the victim, 19-year-old Cathryn Mason, as a naive teen who didn’t use drugs before meeting Forbes, despite a plethora of evidence that showed the teen often used and purchased drugs, including heroin, on her own.

Forbes was arrested last year for the May 2014 death of Mason, who was found dead in Forbes’ bedroom in the Post Falls home where he lived with his parents. There was evidence Mason and Forbes used opiates together, according to court records, and that Mason had previously overdosed on Forbes’ methadone. Forbes was arrested for possession of a controlled substance after authorities found drugs in the house after Mason’s death, but he was not charged with killing his girlfriend until the December 2017 indictment.

In her motion, Taylor said Mason had a history of drug use that was confirmed in interviews with her friends, evidence including heroin that police obtained in a search of her home, and through phone records that show she had made contacts with people who sold her drugs.

“The prosecutor knew that Cathryn had the purchase connection,” Taylor wrote in her motion. “The state ignored data contained in Cathryn’s phone … numerous references to drug use, purchasing drugs and travel plans to obtain drugs.”

Prosecutors kept this evidence from members of the grand jury in an effort to sway the opinion of jurors, she said.

“Not only did the prosecutor allow the jury to think Ryan got the drug, he encouraged this belief,” Taylor wrote.

Deputy prosecutor Stanley Mortensen however, arguing against Taylor’s motion, said Forbes volunteered to police that he had assisted in injecting Mason with the heroin that killed her.

Forbes had consented to a polygraph test where he reportedly told the polygrapher of his involvement in the death of his girlfriend, and when police asked to interview him, he told them that “the defendant and Cathryn had used heroin together on more than one occasion and that (he) had injected Cathryn with a dose of heroin that led to her overdose and death,” according to Mortensen’s brief.

In addition, Mortensen said grand jurors received sufficient evidence to indict Forbes and that exculpatory evidence was presented.

A pretrial conference in the case is set June 21 in Coeur d’Alene.