Kim Sengupta, "Nelson Mandela memorial: ‘Bogus’ interpreter made mockery of Barack Obama’s tribute", The Telegraph 12/11/2013:
The key address in the memorial service for Nelson Mandela was given by Barack Obama, whose words were brought to life for deaf spectators and TV viewers by a “sign language interpreter”, who could be seen gesturing energetically behind the sombre US President.
Yet the man, not only seen by the tens of thousands in Johannesburg’s FNB stadium where the memorial took place on Tuesday, but also by millions across the world on television, was a “fake”, according to Bruno Druchen, the national director of the Deaf Federation of South Africa.
Mr Duchen told the Associated Press “there was no meaning in what he used his hands for”. He and other language experts pointed out that the man was not signing in South African or American sign languages and could not have been signing in any other known sign language because there was no structure to his arm and hand movements. South African sign language covers all of the country’s 11 official languages.
Apparently, the fake interpreter was not a creative gate-crasher, but rather was a fraud who makes money by getting himself hired to provide sign-language interpretation — "Interpreter For Deaf At Mandela Event Called Fake", NPR 12/11/2013:
The man also did sign interpretation at an event last year that was attended by South African President Jacob Zuma, Druchen said. At that appearance, a deaf person in the audience videotaped the event and gave it to the deaf federation, which analyzed the video, prepared a report and submitted a formal complaint to the governing African National Congress party, Druchen said. [...]
Bogus sign-language interpreters are a problem in South Africa because people who know some signs — frequently because they have deaf relatives — try to pass themselves off as interpreters, Parkin said. And those contracting them usually don't know how to sign, so they have no idea the people they are hiring cannot do the job, she said.
"They advertise themselves as interpreters because they know 10 signs and they can make some quick money," Parkin said. "It is plain and simple abuse of the deaf community. They are taking advantage of the deaf community to make money."
I was interested to read that the fraudster's expressionless face was seen as a clue that his gestures had no meaning:
When South African Deputy President Cyril Rampaphosa told the crowd that former South African President F.W. de Klerk was among the guests, the man at his side used a strange pushing motion unknown in sign language that did not identify de Klerk or say anything about his presence, said Ingrid Parkin, principal of the St. Vincent School for the Deaf in Johannesburg.
The closest the man's gestures came to anything in sign language at that point might possibly be the words for "running horse," "friend" or "beyond," she said, but only by someone who signs terribly.
The man also used virtually no facial expressions to convey the often-emotional speeches, an absolute must for sign-language interpreters, Parkin said.
Compare Lydia Callis, the last sign language interpreter to get major press coverage:
Ms. Callis was described as "the antithesis of the stoic mayor" and "much more expressive than [Mayor Bloomberg] is". But as Eric Baković noted ("It just looks so much better in sign", 10/31/2012):
[L]ooking at the videos, I don't see anything other than a (very good) ASL interpreter — in other words, Callis is not doing anything extra special here, she's just doing her job, which is to translate what people are saying into ASL. I understand that there's the contrast with the otherwise somber Bloomberg, and that what is being translated is news about Hurricane Sandy, and that for many folks this may be one of the first times they've seen sign language interpretation up close — but I can't help pointing out here that the hand movements and facial expressions are defining features of ASL (and of other signed languages). The perception that we non-signers have that these hand movements and facial expressions are particularly "animated" and "expressive" is precisely due to our lack of experience with them as linguistic features.
And as Neal Whitman points out in the comments, you can find a clear, cogent, detailed account of (some of) Ms. Callis's facial expressions and body language here: Arika Okrent, "Why do sign language interpreters look so animated?", Mental Floss 11/1/2012.