The man who admitted to killing his wife and then hiding her body in a homemade tomb in their basement has been acquitted of murder, but found guilty of manslaughter.

Allan Shyback, 40, was on trial for second-degree murder in the death of his common-law wife Lisa Mitchell, 31, in 2012. He hid Mitchell's body for two years in the same home where he continued to live with their children.

"It's over, it's done, we can get on with our lives," said Peggy Mitchell, Lisa's mother. "That was the best we could hope for."

Peggy Mitchell embraced Staff Sgt. John Hebert who was involved in searching for her daughter when she was considered a missing person.

Peggy Mitchell John Hebert

Staff. Sgt. John Hebert was in the missing persons unit when Lisa Mitchell disappeared in 2012. Lisa's mother Peggy Mitchell embraces the officer after her daughter's killer was found guilty of manslaughter. (Meghan Grant/CBC)

Shyback testified in his own defence, telling the judge he choked Mitchell because she had threatened him with a knife and he was defending himself. He said after he realized Mitchell was dead, he panicked thinking nobody would believe his story and worried his children might be taken away.

Court of Queen's Bench Justice Rosemary Nation rejected Shyback's claim of self-defence, largely based what he did after he killed Mitchell.

"The post-offence conduct supports the finding that the accused knew that all his actions were not truly done in self defence," said Nation.

"[His] actions here were not all taken in panic; they extended for days, even months after the events." 

Allan Shyback Lisa Mitchell body

Lisa Mitchell's body was found by police two years after she disappeared inside a plastic bin that had been covered by cement in a corner of the couple's basement. (Court exhibit)

A year-long undercover "Mr. Big" sting operation was launched in 2013. During that time, officers befriended Shyback and spooked him into telling them what he'd done with promises to help him escape criminal liability. 

Shyback was arrested after he confessed.

"I thought the undercover investigation was done exceptionally well in this case," said prosecutor Jamie Williams, who added she was "pleased" with Nation's decision.

Shyback was also found guilty of indignity to a body. His lawyer Balfour Der said Shyback was operating in "pure panic" when he hid Mitchell's body. 

"He recognized the optics and what occurred afterwards were really quite serious," said Der. "He's remorseful for everything that happened here."

A sentencing hearing will take place in September.