John Rosen told a Toronto-area court that Shakeil Boothe died on May 26, 2011, though paramedics were only called to the home the following day.
He alleged the boy's father, Garfield Boothe, panicked on finding his dead son and called his own father for advice.
In cross-examining the boy's grandfather, Rosen suggested Burke Boodth — a former police officer in Jamaica — would know "how to clean up a crime scene and stage the death of a little boy."
An emotional Boodth berated the lawyer for casting doubts on his character and "putting (him) through this."
Boodth previously testified his son called him on May 27, 2011, asking to meet in person at the family's Brampton, Ont., home. When he went upstairs to see Shakeil, he realized the boy was dead and immediately convinced his son to call 911, he told the court.
"What was really happening is you knew the boy was dead and dead for a day," Rosen argued.
He alleged Boodth was there to "make sure the scene was cleaned" before his son called 911 — an accusation the grandfather vehemently denied.
Paramedics found Shakeil that afternoon lying in bed, cold, rigid and foaming at the mouth, court has heard. Those who first examined him at the scene testified they believe the boy had been dead for some time.
Forensic photographs presented in court Tuesday showed cuts, bruises and abrasions on his face, arms, shins and back. Some appeared fresh, while others seemed to have scarred over.
The child's father and stepmother, Nichelle Boothe-Rowe, are charged with second-degree murder.
Prosecutors allege Shakeil was kept chained to his bed, beaten and starved in the months before his death.
They also allege the couple moved most of their possessions into storage after finding Shakeil on May 26, and arranged for Boothe-Rowe to take their other child — a baby boy born in September 2010 — across the U.S. border while Boothe stayed behind to deal with the situation.
Crown lawyers said surveillance video from the Brampton City Centre Mall shows Boothe walking into a bank that same afternoon. Bank records indicate Boothe emptied out a bank account he shared with his son, they said.
"Did you tell them to do any of those things on May 26 while Shakeil lay dead at home?" prosecutor Brian McGuire asked Boodth.
"No," Boodth answered.
He also denied having seen any warning signs of abuse during his visits with the family in the months leading up to Shakeil's death.
While he suspected Shakeil had grown jealous of his infant half-brother, who commandeered much of his parents' attention, Boodth said there was no indication the child was being mistreated.
Rosen noted Shakeil was "very sick" at the time and had open sores on his legs as well as welts on his back, but Boodth said he never saw them.
"I don't witness anything," he said. "I would never in my lifetime tolerate anything like that."
He gave conflicting accounts of his relationship with Shakeil, however, at times painting it as a tight bond cemented by frequent visits, long talks and hugs; at other times, he claimed to have only seen the boy five or six times over two years.
He also told police immediately after Shakeil's death that he hadn't seen his grandson since New Year's Eve, despite having seen him at a family birthday party in March.
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