African witchcraft was a "driving force" behind the torture and killing of a 15-year-old boy, a jury has been told.
Kristy Bamu died after suffering 101 injuries on Christmas Day 2010, in a flat in Manor Park, east London.
Expert witness Dr Richard Hoskins has studied the form of witchcraft, known in the Democratic Republic of Congo as "kindoki", for more than 25 years,
He told the court: "In this case the evidence that I've read is something completely feral, it's wild, it's completely out of control.
"It's beyond the normal patterns that exist in the Congo."
Kristy had been visiting London with his siblings and the group were staying at the home of their eldest sister, Magalie Bamu.
During the trial it has been alleged that Magalie Bamu and her partner Eric Bikubi both accused Kristy of being a witch after he wet himself.
Dr Hoskins told the court: "The trigger that seems to occur can be anything deemed to be unusual or out of the ordinary...bed-wetting would be a classic."
He went on to describe how "kindoki" seemed to be the "central strand or driving force" behind the killing.
He said it had moved from a belief in the spirits of ancestors to a perception that living people can be possessed by evil spirits.
Dr Hoskins told the Old Bailey that over 100,000 children in the African country had been abandoned by families after being accused of being possessed.
He said that in the DRC : "It is absolutely standard now, regrettably, for a child to be accused of witchcraft."
Dr Hoskins went on to outline how "deliverance" from witchcraft has also changed over the years.
He said at one time it was enough to have a simple charm or to kill a small animal to exorcise witchcraft, but that deliverance ceremonies can now be far more extreme.
Prosecutor Brian Altman QC asked him whether the rituals that had taken place in the flat were consistent with this phenomenon.
Dr Hoskins confirmed that sleep deprivation and fasting were "totally standard in a deliverance pattern".
Eric Bikubi, 28, admits taking part in the attacks but denies murder due to mental illness. Magalie Bamu who is also 28 denies murder. The trial continues.