The bogus sign language interpreter at the Nelson Mandela memorial service has been accused of being part of a gang who burned two men to death.
Thamsanqa Jantjie was among a group who found the men with a stolen television and burned them to death in 2003, a relative and three friends claimed.
They said tyres were placed around the men's necks and set ablaze. Unlike two other suspects who went to trial in 2006 for the killings, they said Jantjie never did because he was determined mentally unfit.
The men, including one of Jantjie's cousins, insisted on anonymity because of sensitivity surrounding the bogus signing, which embarrassed South Africa's government.
They say Jantjie was institutionalised and then returned to his neighbourhood on the outskirts of Soweto.
After that he began sign language interpretation at events for the governing African National Congress Party.
Jantjie said he has schizophrenia and hallucinated, seeing angels while gesturing incoherently just feet away from President Barack Obama and other world leaders during the Mandela ceremony. Experts said his arm and hand movements were mere gibberish.
Jantjie has admitted being violent in the past "a lot" but declined to provide more details and blamed his violence on his schizophrenia, for which he said he was institutionalised for 19 months in a period that included time during 2006.
The cousin and the three friends said the killing of the suspected thieves occurred within a few hundred yards from Jantjie's home.
"Necklacing" with a tyre was a method of killing that was fairly common during the struggle against apartheid by blacks on blacks suspected of aiding the white government or belonging to opposing factions. The method was also used in tribal disputes in the 1980s and 1990s. While people who encounter suspect thieves in South Africa have been known to beat or kill them to mete out punishment, necklacing them has been rare.