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

The former partner of a man accused of murdering a five-year-old girl learned about the killing from their son, a Winnipeg court heard Friday.

Loretta Stevenson was the first witness in the trial of Karl McKay and his common-law wife Samantha Kematch. The Fisher River couple have been charged with first-degree murder in the death of Phoenix Sinclair, Kematch's daughter.

Stevenson, who had two children with McKay during their 12-year relationship, said during testimony Friday that their two boys would often visit their father, a long-haul truck driver who would occasionally take the boys with him on the road.

The court heard that after returning from one of those visits, one of the boys was acting strangely. When Stevenson asked him what was wrong, the boy said: "'My dad killed somebody.'"

Both McKay and Kematch have pleaded not guilty.

Stevenson described McKay as a violent man who tried to kill her on two separate occasions. She recounted having her head stuck in a toilet, as well as being kicked and punched.  

It is believed Phoenix Sinclair, 5, was killed in 2005, although her remains were not found until months later. Her death sparked a massive review of Manitoba's child welfare system.

Crown attorney Rick Saull said during opening statements this week that the little girl suffered months of abuse before dying at the hands of her mother and the mother's boyfriend. After the girl died, he said her body was wrapped in plastic and buried in a wooded area near a landfill using a neighbour's shovel.

The couple has been accused of covering up the slaying before applying for welfare in the dead child's name.

A second witness who testified Friday, Stephanie Roulette, told the court that McKay and Kematch asked her to bring her daughter over one day in 2006. 

Roulette, who is McKay's niece, said the couple told her to have her daughter pretend she was Phoenix to fool welfare officials.    

The trial is expected to last until mid-December.

With files from the Canadian Press