Officers noticed "reddish-brown stains" on Shakeil Boothe's mattress and sheets, on the baseboards of his room and on a boy's T-shirt crumpled under his bed, Det. Peter Duivesteyn of Peel police testified.
Forensics experts examined the family's home in Brampton, Ont., for three days after paramedics found Shakeil's lifeless body there on May 27, 2011.
"We had noted when we had gone in on the 28...some blood spatter in the victim's room," as well as just outside his door, the detective said.
Shakeil's father, Garfield Boothe, and stepmother, Nichelle Boothe-Rowe, are both charged with second-degree murder.
Prosecutors allege Shakeil actually died on May 26 from a violent incident combined with months of abuse and starvation.
They say the boy, who came to Canada from Jamaica in 2009 to live with his father, was kept chained to his bed except for when he went to the bathroom, showered or when relatives visited.
Duivesteyn told the court officers seized several items from the home, including belts, a strap, a computer hard drive and men's clothes with spots "believed to be blood."
All were sent for DNA testing at the Centre for Forensic Science in Toronto, he said.
The results were not presented in court, but Crown lawyers said in their opening statement the blood belonged to Shakeil.
The detective said he had been instructed to look for a belt with a "loop" buckle after investigators found U-shaped marks on Shakeil's body.
Pictures shown in court show Shakeil lying dead in his bed, with white foam coming out of his mouth.
There are cuts, bruises and abrasions — both fresh and scarred over — on much of the boy's body.
Paramedics have testified they believe he had been dead for some time when he was found.
Police also seized several bags of a "green leafy substance" that appeared to be marijuana from the house and backyard.
Documents, including a hospital receipt for a sling for Shakeil and bank card in his name, were also seized.