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Paul Hoffman, a former acting High Court judge in South Africa, was quoted by the BBC as saying that option was very unusual, but could be arranged through an inter-governmental deal.
A UK Ministry of Justice spokesman said the department had prisoner transfer agreements with various countries but not with South Africa. However, that could change in the future.
"We hope to get more agreements with other countries and one of them may be South Africa," he said.
Anni Dewani, 28, from Sweden, was shot when a taxi in which the couple were travelling was hijacked in Gugulethu in Cape Town last November.
South African prosecutors say they have evidence that Dewani paid a taxi driver to arrange the murder and want him extradited to stand trial.
Dewani, 31, from Bristol, denies any involvement in the killing.
Hoffman, a director of the Institute for Accountability in Southern Africa, said that if extradited, it would be likely that Dewani would be put on trial along with his co-accused, Mziwamadoda Qwabe, 25, and Xolile Mngeni, 23, at the High Court in Cape Town.
He faces charges of murder, conspiracy to commit murder, robbery with aggravating circumstances and obstructing the administration of justice.
It is also possible that Dewani could be tried in the UK, Hoffman added.
Care home owner Shrien Dewani is said to be suffering from severe post-traumatic stress disorder and depression, and has fought extradition, arguing he is too unwell to face trial.
In August, a judge ruled that Dewani could be extradited to stand trial.
Sitting at Belmarsh Magistrates' Court in London, District Judge Howard Riddle said he was satisfied Dewani would receive the appropriate mental health care in South Africa.
Judge Riddle also said he was satisfied that Dewani would be held in a prison with good facilities and that he would be kept in a single cell.
"The conditions in South African prisons are atrocious," Hoffman said. "There is gross overcrowding, corruption, routine rape of inmates, intimidation, HIV/AIDS, TB. Gangs rule prisons.
"I'm sure he [Dewani] would be a kid gloves prisoner because of his high profile and his nationality, but to spend a long sentence in a prison hospital is a pretty ghastly prospect."
Hoffman said the option of spending time in a private hospital in South Africa under guard could also be available to Dewani.