NORTH COAST, Calif. – A Hidden Valley Lake man on Thursday pleaded guilty in Mendocino County Superior Court to manslaughter for the December death of his wife, who was killed by a sheriff’s deputy as the two were involved in a standoff with law enforcement at a Ukiah hotel.

Joseph Charles Mantynen, 32, pleaded guilty to felonies including voluntary manslaughter, assault with a firearm on a Mendocino County deputy sheriff, a separate assault with a firearm on a Sonoma County deputy sheriff and burglary in the first degree, the Mendocino County District Attorney’s Office reported.

Officials said Mantynen also admitted that he had personally used a firearm in the commission of the conduct underlying the conviction for voluntary manslaughter.

Mantynen entered the change of plea on Thursday as part of an agreement reached with the Mendocino County District Attorney’s Office.

Mantynen and an accomplice, his parolee wife, Mary Elizabeth Windham, together burglarized the home of Mantynen's grandmother in Sonoma County on Dec. 20. Investigators from Sonoma County tracked the couple to Ukiah and found them hiding out in a State Street motel on Dec. 21.

Rather than surrender, Mantynen later confessed to interrogators that the couple had agreed to resist arrest and, if escape was not in the cards, to die together by means of "suicide by cop."

During the early stages of the stand-off, Mantynen pointed his rifle at and threatened a Sonoma County deputy sheriff.

In doing so, Mantynen committed what is known in the law as a “provocative act” that allowed for the use of deadly force by the threatened deputy.

Fearing for his own safety and that of his team, the Sonoma County deputy discharged his firearm at Mantynen but the shot missed.

The out-of-county law enforcement officers surrounding the motel room were quickly reinforced by the Ukiah Police Department, as well as the sheriff's special weapons and tactics unit.

As the stand-off lengthened, Mantynen again pointed his rifle at and threatened law enforcement, this time a Mendocino County deputy sheriff.

Apparently as part of the couple's death plan, this act by Mantynen was provocative that allowed for the use of deadly force by the local deputy.

Fearing for his own safety and that of others, the Mendocino County deputy discharged his firearm at Mantynen.

That shot went through Mantynen's bulky clothing, missing the defendant's body, hitting Windham, who was also participating in the stand-off and verbalizing death threats at law enforcement.

After his wife was fatally hit and fell to the ground, Mantynen surrendered to law enforcement.

Following his review of crime reports from the multiple agencies, Mendocino County District Attorney David Eyster elected to charge Mantynen with being responsible for the death of Windham pursuant to the provocative act doctrine, a legal theory of homicide prosecution which applies when someone commits an act that provokes someone into killing someone else.

Pursuant to the case resolution as worked out by Mantynen, his attorney and District Attorney Eyster, Mantynen will be sentenced to a stipulated commitment on March 28 of 26 years, four months in state prison.

Because of the violent characterization of the crimes involved, the good time/work time credits Mantynen may earn in prison against his total sentence will be limited to 15 percent. Eyster also required that Mantynen waive all jail credits from the date of his arrest until the date of sentencing.

The prosecutor handling this matter will continue to be Eyster. The investigating law enforcement agencies are the Sonoma County Sheriff's Department, the Mendocino County Sheriff's Department, the Ukiah Police Department, the California Department of Justice forensic laboratory and the district attorney's own investigators.

The judge who accepted the change of plea was Mendocino County Superior Court Judge John Behnke.

Judge Behnke will formally sentence Mantynen at 9 a.m. March 28 in Department H of the Ukiah courthouse.