An interpreter on South Africa's SABC TV shows the
signing which should have been used
The sign language interpreter accused of using fake hand signals at Nelson Mandela's memorial has said he suffered a schizophrenic episode.
Thamsanqa Jantjie, 34, told South African media he "started hearing voices" and began hallucinating.
Deaf viewers at Tuesday's memorial service complained he was a fraud.
Mr Mandela died last week at the age of 95 and will be buried on Sunday. His body is lying in state in Pretoria, with thousands queuing to pay respects.
South Africans are queuing to pay their respects to Mr Mandela
For many, glimpsing him in his coffin was an emotional experience
But others were in more jovial mood, preferring to celebrate Mr Mandela's life
Mr Jantjie said he worked for a company called SA Interpreters, where he is a senior interpreter.
During the memorial, he was employed to stand on the stage next to key speakers such as US President Barack Obama and Mr Mandela's grandchildren, translating their eulogies.
Speaking to Johannesburg's Talk Radio 702, Mr Jantjie
said that he had been interpreting "for years"
His performance was watched on television by millions of people worldwide.
But he said that during the event, he lost concentration because of voices in his head.
"There was nothing I could do. I was alone in a very dangerous situation," Mr Jantjie told Johannesburg's Star newspaper.
"I tried to control myself and not show the world what was going on. I am very sorry. It's the situation I found myself in."
But in a subsequent radio interview, he said he was happy with his performance.
"I've interpreted in many big events," he told Talk Radio 702. "I think I've been a champion of sign language."
Mr Jantjie defends his performance to Johannesburg's Talk Radio 702
Mr Jantjie's performance at the memorial provoked anger among South Africa's deaf community.
During the broadcast, Wilma Newhoudt-Druchen, the country's first deaf female MP, tweeted: "ANC-linked interpreter on the stage with dep president of ANC is signing rubbish. He cannot sign. Please get him off."
The ANC (African National Congress, the ruling party) was in charge of the memorial, along with the government.
It appears that Mr Jantjie has worked for the ANC before, as footage from two big ANC events last year show him signing on stage next to President Jacob Zuma.
The South Africa's Translators' Institute said there had been complaints over Mr Jantjie's work before, but the ruling party took no action.
The government is investigating what happened, but on Wednesday it said it "wishes to assure South Africans that we are clear in defending the rights and dignity of people with disabilities".
After Mr Mandela's body has lain in state for three days, the military will fly him to the Eastern Cape from Air Force Base Waterkloof in Pretoria.
A military guard of honour will welcome the arrival, and the coffin will then be placed on a gun carriage and transported to a hearse.
Mr Mandela's body will then be taken to his home village of Qunu, where the Thembu community will conduct a traditional ceremony.
A national day of reconciliation will take place on 16 December when a statue of Mr Mandela will be unveiled at the Union Buildings.
Big screens have been set up across South Africa to show the planned national events.