While British High Court judges dismissed that part of Dewani's argument, concerns about potential torture and abuse in detention are warranted, Erfani-Ghadimi said.

South Africa is a signatory to the U.N. Convention on Torture, but it has yet to ratify it, so such abuses have not been criminalized.

"A legacy of apartheid is that prison cells are still unfortunately a place where prisoners can be abused," Erfani-Ghadimi said.

Amnesty International's Annual Report 2012, which looked at human rights around the world, also said that a draft law to make torture a criminal offense had not been presented in South Africa's parliament by the end of the year.

Human dignity

Nevertheless, said Erfani-Ghadimi, the problem doesn't lie in South Africa's laws so much as in the ability of the justice system to cope with the number of inmates in the system.

South Africa's constitution and its bill of rights, with regard to prisoners' rights, are among the best in the world, she said. "Unfortunately, that doesn't necessarily translate into practice."

She says she thinks conditions are improving, however, thanks in part to the strength of those constitutional rights and the work of civil society organizations campaigning for change.

And Pistorius, if he ends up spending time on remand or is eventually convicted and jailed, should find that his particular medical needs as a double amputee are taken into account, she said.

This could mean that he is sent to a prison with better medical facilities or wheelchair access, she suggested.

According to the bill of rights, prisoners are entitled to "be detained in conditions that are consistent with human dignity, including at least exercise and the provision, at state expense, of adequate accommodation, nutrition, medical treatment."

Correctional Services Department spokesman Koos Gerber said South Africa's detention facilities, whether for remand prisoners or those serving prison terms, "can accommodate people with any disabilities."

"We have a general problem of overcrowding but we have learned to live with it," said Gerber, adding that extra bunks have been added to make sure all remand prisoners have a bed. Hospital facilities are also available at all times, he said.

According to official figures for 2011 to 2012, there were 158,790 prison inmates in South Africa, a nation of nearly 52 million, of whom about 30% were on remand awaiting trial.

This compares with about 2.2 million people in prisons or jails in the United States at the end of 2011, according to U.S. Department of Justice figures. Crowding in U.S. prisons stood at 39% over capacity in 2011, according to a Government Accountability Office report.

Long wait for trial

Erfani-Ghadimi blames systemic problems for South Africa's overcrowding. One issue is that police are quick to arrest people, she said, and they have only 48 hours from arrest to bring charges.

After they are charged, many suspects cannot afford to make bail or hire a lawyer and so are forced to spend months or even years behind bars awaiting trial, she said.

Investigations are often poorly run and courtrooms can be overcrowded, adding to the hurdles faced by those on remand, she said.

"Because the system is cumbersome and slow, there's a lot of people stuck waiting -- and that means the conditions are not by any means ideal," she added.