Violence inflicted on a teenager accused of being a witch was "completely feral" and "out of control", a court heard today.
Kristy Bamu, 15, was beaten and tortured before he drowned in a bath in his sister's east London flat on Christmas Day, 2010.
Today witchcraft expert Dr Richard Hoskins told a jury at the Old Bailey that the attack went way beyond accepted practices in Democratic Republic of the Congo (DRC), where Kristy's family are originally from.
He said: "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's sister Magalie Bamu and her boyfriend Eric Bikubi are accused of murdering him because they thought he was affected by an evil force called kindoki.
Dr Hoskins told the court that Kristy wetting himself could have been the trigger for the alleged violence.
He said: "The trigger that needs to occur for people to think someone is possessed by kindoki can be anything out of the ordinary. Bed-wetting is a classic example of this."
Other factors could have been Kristy's older brother Yves' autism, an allergic reaction that made Yves' lip swell or their younger brother having problems getting out of bed, the court heard.
Belief in kindoki is "all pervasive" in Congolese society regardless of someone's standard of education or social class, Dr Hoskins told the jury.
It is believed that the malevolent power can possess someone, and that they can use it to control other people, he said.
Over the last 15 years the "child witch phenomenon" has emerged where children are accused of being possessed.
Dr Hoskins told the court: "It's absolutely standard regrettably to accuse a child in the DRC of having witchcraft...Nobody would raise an eyebrow at the suggestion in the DRC."
Ways to purge a child include fasting, all night vigils and using water to purify those involved, he said.
The worst levels of violence he had seen were a stinging substance being thrown in a child's eyes, one being shaken and another being given a shallow cut with a razor blade.
Bikubi, 28, of Hathaway Crescent, Newham, east London, has admitted manslaughter on the grounds of diminished responsibility but denies murder. He also denies committing assault causing actual bodily harm on two of Kristy's sisters.
Magalie Bamu, also 28 and of the same address, denies murder and two counts of ABH.
The trial was adjourned until tomorrow.