Tom Parmenter, Sky News correspondent
The victim, Kristy Bamu, was found drowned with 101 different injuries on Christmas Day 2010 in a flat in Newham, east London.
He had travelled with his siblings from Paris to spend the holiday with his older sister Magalie Bamu.
Opening the trial at the Old Bailey, prosecutor Brian Altman QC told the jury that when Kristy was found: "His face and his head were covered in deep cuts and bruising, his arms and back bore deep cuts and lacerations, there were teeth missing or loose in his mouth.
"It was plain that Kristy had been the victim of a prolonged attack of unspeakable savagery and brutality" he added.
He said Magalie Bamu and her partner Eric Bikubi, both 28, had been abusing members of the family for four days.
The prosecutor argued that while the youngsters had enjoyed their first few days there, "the mood started to turn sour".