New London — A three-judge panel on Monday ruled David McKeever not guilty by reason of insanity in the fatal 2015 stabbing of his longtime partner, Delma Murphy, at their home here.

The ruling means that instead of prison, the 50-year-old McKeever is likely to be committed to the Whiting Forensic Hospital, which maintains a maximum security facility for patients with psychiatric problems and have been convicted of serious crimes.

A hearing is tentatively scheduled for Dec. 21 in New London Superior Court when the Psychiatric Security Review Board will make a recommendation to a three-judge panel on the length of McKeever's commitment.

McKeever faces up to 60 years at the psychiatric hospital. The three-judge panel, composed of judges Arthur C. Hadden, Barbara Bailey Jongbloed and Hunchu Kwak, will decide on the length of McKeever’s commitment.

The state had pursued a murder charge in the case and state prosecutor Lawrence J. Tytla said the state, through evidence and witnesses presented at trial, met its burden of proving McKeever committed the crime. The trial was held in New London Superior Court over the course of the past week.

Defense attorney Christopher Duby successfully argued that McKeever, at the time of the killing, lacked the capacity to appreciate the wrongfulness of his conduct or control his conduct because of a mental disease or defect. Tytla, in his argument before the judges, said he expressed skepticism that the defense presented enough evidence to meet its burden.

McKeever has a history of mental illness and is hearing- and sight-impaired because he was born with a congenital disorder known as Usher Syndrome, according to court documents and testimony.

He had lived with Murphy, 46, for 11 years and referred to her as his wife.

Murphy’s body was discovered by a friend, Pamela Cekala, on Nov. 18, 2015. Concerned for her welfare, Cekala visited the couple’s home after unsuccessfully trying to contact Murphy for five days. She found the house at 53 Cole St. in disarray and McKeever initially told her Murphy was upstairs sleeping and later that he thought he had killed her.

Cekala discovered Murphy’s body in the upstairs bedroom where there was blood on the walls, door frames and other surfaces. A bloodied hunting knife was on the floor outside the bedroom door.

An autopsy revealed Murphy died of multiple cuts and stab wounds to her chest, abdomen, arms and legs. The wounds were deep enough to penetrate her heart, both lungs, liver and spleen. It was unclear how long she had been dead.

g.smith@theday.com