Skeptic Project

http://www.telegraph.co.uk/news/worldnews/africaandindianocean/southafrica/10510455/Nelson-Mandela-memorial-interpreter-was-a-fake.html

A mystery South African man who acted as a sign-language interpreter at Nelson Mandela's memorial service was a "fraud" who simply made "childish hand gestures" for hours as he stood on stage.
Deaf groups say the man, who has not yet been identified, made no sense in any language to those relying on him around the world, and did not seem to know the recognised signs for South Africa, Mr Mandela's clan name Madiba, President Jacob Zuma or former President Thabo Mbeki.

[...]

While some South Africans took to Twitter to claim the man had been signing in a South African language such as Xhosa or Zulu, Mr Buxton said he was purely making "childish hand gestures and clapping, it was as if he had never learn a word of sign language in his life".
"It was hours of complete nonsense," he said. "He is clearly a fraud who wanted to stand on stage with big and important people. It's quite audacious if you think about it," he said.
"It is incredibly disrespectful and hurtful to the deaf community."

elohel

He claims he was hallucinating when he did this.

http://www.usatoday.com/story/news/world/2013/12/12/mandela-sign-language-interpreter-thamsanqa-jantjie/3995875/

He's also been accused of being a rapist, murderer, and kidnapper.

http://www.enca.com/south-africa/interpreter