OSHAWA, Ont. — The end of Keagan Davis' short life must have been hell.

The prosecution painted a gruesome picture of the two-year-old's fate at the beginning of the trial for his mother's live-in boyfriend, who is accused of second-degree murder, assault causing bodily harm and aggravated assault.

Michael Monckton, 28, has pleaded not guilty to all charges.

Crown attorney Paul Murray told the 12-member jury that an autopsy found Keagan had "multiple severe" injuries that included bruises, broken bones and internal bleeding.

Some of those injuries were fresh and some had healed or were healing, but all were suffered at the hands of Michael Monckton, Murray alleged as he outlined the Crown's case.

Monckton was watching Keagan on Jan. 5, 2010, as he often did while his girlfriend was at work. It's alleged Leigh-Ann Cooper arrived home that morning to find Monckton performing CPR on her son, who had stopped breathing.

In court Wednesday, the Crown played the frantic 911 call subsequently made by Cooper.

"Help us!" she was heard crying as the 911 operator gave CPR instructions.

Police officers could be heard arriving at the home moments later and paramedics were on the scene almost simultaneously.

Const. Matt Forget, the Crown's first witness, had only been on the job 18 months and it was his first call involving a child with no vital signs.

He testified Cooper was "hysterical" when he entered the home and Monckton was positioned over Keagan as though he was performing CPR.

But Forget said he never actually saw Monckton delivering chest compressions or breaths to the lifeless toddler, who he recalled being "bluish in colour."

It's expected defence attorney Ray Boggs will argue Keagan's injuries were inflicted during CPR.

Monckton was arrested two days after Keagan's death and has been in jail since.

His trial is expected to last six weeks, during which time the jury will hear from medical experts.

Family members will also be called to testify.

The trial before Judge Alex Sosna resumes Thursday.