The body of Phoenix Sinclair, seen here in an undated photo, was discovered in 2006 on the Fisher River reserve.

A Manitoba couple found guilty last year of killing five-year-old Phoenix Sinclair in 2005 returned to court on Tuesday to appeal for a reduced sentence.

Sinclair's mother, Samantha Kematch, and stepfather Karl McKay were convicted of first-degree murder and sentenced to life in prison in December. They are not eligible for parole for 25 years.

In separate briefs filed with the Court of Appeal, Kematch and McKay argue they were unfairly convicted, adding they should have been tried separately instead of together.

During the trial, defence lawyers did not deny the abuse but argued there was not enough evidence to convict the couple of first-degree murder. The defence teams suggested that manslaughter may be a more appropriate sentence because it was not clear who had delivered the final fatal blow to Phoenix.

Sinclair was killed in June 2005 in the basement of a home on the Fisher River First Nation, about 180 kilometres north of Winnipeg.

She was wrapped in plastic and buried in a shallow, unmarked grave near the garbage dump of the reserve.

Girl may have hid in basement: lawyer

On Tuesday, one of the lawyers appealing the convictions said Sinclair may have sought refuge there. Mike Cook suggested to the Manitoba Court of Appeal that Sinclair had been abused by Kematch and McKay so often, she may have stayed in the basement voluntarily to get away from them.

The couple was found guilty of first-degree murder, instead of lesser charges, because the jury ruled they had confined Sinclair in the basement. Under the Criminal Code, a slaying committed while forcibly holding someone elevates the crime to first-degree murder rather than second-degree murder or manslaughter.

Cook said there were no locks on the doors, and no doors to the basement where she was kept.

"There is some doubt as to whether the parents forced her down there," Cook said. "Perhaps she liked to be away from them."

He argued that Sinclair may have been afraid to venture upstairs because she was told not to, but the lack of any physical restraint means the conviction must be reduced to second-degree murder or manslaughter.

His theory received a rough reception from the three appeal judges, one of whom said he had a hard time believing a young girl would want to stay in a basement away from her parents and siblings.

"I have a great deal of difficulty with that," Justice Martin Freedman said.

The judges pointed to trial evidence that showed Phoenix had been barricaded at one point behind a washer and dryer. That evidence came from only one witness during the trial, Cook said, and it is unclear whether that alleged confinement can be linked to her death.

Crown attorney Rick Saull urged the judges to reject Cook's argument. "[Phoenix] was down there because she was bloody well told to stay there, and she wasn't coming up," he said.

The appeal hearing is set for Tuesday and Wednesday.

Sinclair had been in and out of foster care for most of her life until Kematch regained custody about a year before the girl's death. A child welfare worker checked on the family in early 2005 but didn't see Sinclair during the visit, and no one ever followed up on the case.

Body not found for nine months

No one outside Sinclair's immediate family knew she was missing until RCMP received a tip the following year. One of McKay's teenage sons told authorities about the abuse of Sinclair he had witnessed.

Her body was found in March 2006, after police laid charges against Kematch and McKay.

McKay later showed RCMP the burial site.

During the trial in 2008, the court heard Kematch and McKay routinely beat Sinclair with their fists, feet and metal bars, and forced her to eat her own vomit. Sinclair was also choked until she passed out and was shot with a pellet gun.

The court was also told she had broken bones throughout her body when she died.

Before her body was found, McKay and Kematch continued to list Sinclair as a dependent to collect welfare payments. In early 2006, Kematch tried to pass off another child as Sinclair to child welfare workers and was arrested.

The province has ordered a judicial inquest, specifically because Sinclair was in care before her death. That can't begin, however, until after the appeals process is exhausted.

Former foster mother outraged

Sinclair's former foster mother is outraged about the appeal by Kematch and McKay.

"I think it's ludicrous because we don't feel that they're responsible — that they're accountable — for anything," Kim Edwards said outside the Winnipeg Law Courts over the noon hour.

"I raised that little girl for three years, and she wasn't a handful, she wasn't a bad baby, she wasn't a baby that needed to be disciplined. When you told her once to do something, she did it."

When was asked what she wants to see happen, Edwards said, "I just want the verdict to stand and the sentence to stand. We wouldn't be satisfied with second-degree murder or manslaughter. We wouldn't be complacent with that at all."

With files from The Canadian Press