BRAMPTON, Ont. -- A father and stepmother knew the escalating abuse and deprivation they inflicted on the man's frail and sickly son would likely lead to the boy's death, a Crown lawyer said Thursday in pushing for a murder conviction.

It's unclear whether Garfield Boothe or his wife Nichelle Boothe-Rowe carried out the attack that ended Shakeil Boothe's life, but both were responsible for the months of abuse that sent him on a "downward spiral" to his death, Brian McGuire told a Toronto-area court.

Shakeil, 10, was chained to his bed "for months on end," fed so little he grew emaciated and regularly beaten with a belt until he bled, his injuries untreated and uncared for, McGuire said.

"His two parents denied him basic medical care because to do so would expose their mistreatment of him," he said.

Paramedics found Shakeil's cold, lifeless body at the family's home in Brampton, Ont., on May 27, 2011, but both his father and stepmother testified he died a day earlier. They told the court they believed he had died from a particularly bad cold.

Court has heard autopsy results showed Shakeil suffered heavy repeated blows that caused widespread internal bleeding and overwhelmed his weakened body. He died "minutes to hours" later, the autopsy showed.

The couple is charged with second-degree murder, but defence lawyers have argued only the person who delivered the final beating should be convicted on that charge.

The other could instead be found guilty of manslaughter, though Boothe-Rowe's lawyer has argued she should be acquitted because she feared her abusive husband would lash out if she intervened.

Boothe and his wife have pointed the finger at each other through their lawyers, with each saying the other had motive and opportunity.

In his closing arguments Thursday, McGuire argued both should be convicted of murder, regardless of who committed the last assault.

"Shakeil's death cannot be separated out into different causes," he said, noting it was the "cumulative effect" of the abuse and the beating that pushed the boy over the edge.

No specific time of death has been established, so neither accused can be ruled out in the deadly attack, he said.

However, Boothe's admission that he frequently disciplined Shakeil by hitting the boy on the shoulders, legs and knees makes him a more likely culprit, the lawyer said.

That last beating was "the continuation of a pattern of abuse, of serious abuse, by Garfield Boothe," McGuire said, but that should not let his wife off the hook.

A person can also be found guilty of murder if they help carry out the killing or encourage another to do it, or if they agree to commit an unlawful act they know is likely to end in death.

Boothe-Rowe was "complicit" in the abuse and starvation of her stepson and did nothing to help him "in a meaningful way," the prosecutor said.

"She knew that Shakeil was eventually going to be killed. She stood by and let it happen."

Her defence that she held back out of fear "doesn't fly," he said.

Her husband had a history of domestic violence, but hadn't hit her since the birth of their infant son, and there is no evidence he threatened to hurt her if she spoke out, he said.

Boothe-Rowe was also alone with the children all day and could easily have called police while her husband was at work, he said.

After the boy died, the couple acted "in lock step" to cover it up, McGuire said. Neither called 911. They instead concocted a series of lies to tell police and children's aid, and arranged to remove evidence from their home, he said.

Boothe-Rowe then fled to the U.S. while her husband considered making a similar escape, he said.

"Are those the actions of people who believe Shakeil died of a cold? Or are those the actions of people who participated in his death?"

The jury is expected to begin deliberating late next week.