Kenneth Raymond Annack, convicted of murdering a man who Annack said he thought had raped his wife, was sentenced to life in prison yesterday in Prince George's County Circuit Court.

Annack, 38, who was also convicted by a jury last November of carrying a dangerous weapon, will be eligible for parole in 12 1/2 years.

There was prosecution evidence that Annack's wife, Catherine, 34, had spent the night with the victim, Danny Wayne Ward, 30, the day before Ward was killed in August 1981. But Assistant State's Attorney Deborah A. Johnson contended during Annack's trial that Catherine Annack had not been raped.

Annack testified that he and his wife went to Ward's home in Laurel where, Annack said, he intended to ask Ward "what the story was." A prosecution witness testified, however, that when Ward came to the door of his home, Annack asked "Are you Danny Ward?" and fired when Ward said he was.

Annack, who was sentenced yesterday by Judge Audrey E. Melbourne, denied that he fired the blast that killed Ward and suggested in his testimony that Catherine Annack shot Ward after Ward called her "a whore."

According to testimony at Annack's trial, the couple traveled around the country sleeping in a tent until they were arrested in front of Graceland, Elvis Presley's mansion in Memphis, about a month after Ward was killed.

Catherine Annack had also been charged in an indictment with first-degree murder and carrying a dangerous weapon.

Within hours after her husband's conviction in November, however, she pleaded guilty to a lesser charge of assisting her husband's flight from Maryland after the murder and was placed on three years probation, with credit for 60 days she had already spent in jail.