A Manitoba man accused of murdering his wife while their young sons slept said he was devastated when he learned she was killed in their own backyard.

Former political adviser Mark Stobbe sobbed Friday as he testified for the second day in his own defence at his second-degree murder trial in Winnipeg.

"It was confirmation of my worst fears," he cried as he recalled being told by his sister-in-law where Beverly Rowbotham had been slain.

"What it meant was I'd been 50 or 60 feet away when she was killed. What it meant was I should have been able to stop it. What it meant was I was completely useless."

Stobbe then put his head in his hands and sobbed.

He has already testified that he didn't kill Rowbotham in October 2000, move her body or clean up the outside of their St. Andrews home, where the Crown alleges she was bludgeoned to death with a hatchet.

He said he suspected his wife was killed in the backyard because police were focused there and had seized tree stumps.

"To me, the seizure of the stumps was confirmation ... something had happened in the backyard," Stobbe said.

"I spent a lot of nights looking out windows, wondering whether I was watching TV while she was getting killed in the backyard ... I spent many sleepless nights wondering about that."

The Crown is arguing that Stobbe killed his wife, stuffed her body in a car, drove it to a parking lot 15 kilometres away in Selkirk, then bicycled home.

The Crown alleges the backyard was hosed down following the murder. The prosecution has produced DNA evidence that includes small blood drops, hair clumps and tiny bone fragments, some of which have been shown to have come from the victim.

The evidence was found in the backyard and garage.

Stobbe told the jury Thursday his wife decided to return to the grocery store, where she had been earlier that day with their young son, to do some more shopping.

He said he fell asleep in his son's bed and woke up around 2 a.m. to find his wife hadn't returned. Rowbotham's body was found a few hours later in the back seat of one of the family's cars. Her head had been bludgeoned.

Under cross-examination, the Crown suggested Stobbe added 20 new details since he gave a statement to police following his wife's murder. Crown attorney Wendy Dawson said Stobbe has had years to rehearse what to tell the jury and hasn't given any "off-the-cuff" answers when questioned by his lawyer.

Stobbe said he knew his lawyers would take him through the events surrounding his wife's death.

"What has caught me off guard was the intensity of the emotional reaction that still wells up from time to time," Stobbe said. "I thought my soul and heart had pretty much scabbed over . . . but the trial has picked away at those scabs."

He said he was in a state of shock after Rowbotham's body was discovered but did his best to help police catch her killer.

"I was doing the best I could then and I'm doing the best I can now."

Dawson questioned Stobbe extensively about Rowbotham's engagement ring and her jewelry collection. While he filed an insurance claim on the car Rowbotham was found in, Dawson pointed out he didn't file one on her engagement ring, which contained an expensive diamond.

"I suggest you never made an insurance claim on those rings because you removed them from her fingers after your brutally murdered her," Dawson said.

"No," Stobbe said calmly.

The ring was different to the car since it was "a reminder of our marriage and our time together."

Stobbe bristled when the Crown suggested he and his wife had marital problems which they kept private. The two went to marriage counselling when they weren't "enjoying each other's company" but didn't have significant problems, he said.

"We had no particular issues to discuss with anybody. I have trouble remembering any significant argument."

Stobbe joked about his physical appearance Thursday and said the most he had ever biked at the time was to the mailbox and back. But Dawson said Stobbe was physically active especially at university. Stobbe said he did bike often in university and actually bicycled from North Battleford, Sask., to Kamloops, B.C.

"But I was younger and in considerably better shape at that time," he said.

Earlier in the day, Stobbe told the jury his emotional state was hard to describe after his wife's death. While the Crown described him as "rational" and articulate just hours after finding out, Stobbe said he was trying to keep himself together to "provide police with the assistance they were asking for."

"I felt that I needed to be as open and forthcoming and complete as I possibly could be."

He said he was kept in the dark about details of his wife's murder.

"All of us were starved for information, desperate for information," he said. "Police, for understandable reasons, were saying very little."

He arranged a memorial service for Rowbotham in Regina several days after her death. Stobbe said friends were urging him to get a lawyer and make arrangements for his young sons in the event of his arrest.

He also noticed a police car stationed at the end his driveway around the clock. Investigators had set up tarps in the backyard.

"It was profoundly disconcerting. I assumed they'd found something troubling in the backyard but I had no idea why or where."

Police took most of his clothes and a commemorative rifle given to him by his father. In December, officers came back and placed him under temporary arrest so they could search the house, he said.

They took his wedding ring, his glasses and the tree stumps from the backyard.

Stobbe said he last spoke to police in the spring of 2001 and didn't hear from them again until he was arrested at work in May 2008 after he'd moved to Saskatoon.