Funny old thing, the truth. Vaclav Havel wrote that the truth is not simply what you think it is; it is also the circumstances in which it is said and to whom, why and how it is said.

Is it true that the head of the National Prosecuting Authority Bulelani Ngcuka was a spy for the apartheid-era security forces? Ask all you want, there is really no way of telling for sure.

Those who may know, aren't telling. And those who are telling, have such obvious axes to grind, it is hard to credit their tales.

Any number of people could have leaked the allegations about Ngcuka. Deputy President Jacob Zuma knows the intelligence structure intimately and is at war with Ngcuka. Another possibility might be Mo Shaik, former spokesman for the National Intelligence Agency and brother of Durban businessman Schabir Shaik, who has been charged with corruption by the Scorpions.

Another might have been former transport minister Mac Maharaj, who is also involved in an imbroglio involving the Scorpions. Maharaj was quick to confirm the allegation that an investigation was done by the African National Congress (ANC) in the late 1980s which suggested Ngcuka may have been an apartheid agent.

The report was not absolutely conclusive, but it was part of a broader investigation into spies called Operation Bible. But it tantalisingly provided the spy's number RS452.

What are the specific allegations? Maharaj declined to discuss the issue with Business Day, but his case was fairly fully explained in a radio interview on SAfm this week.

In the interview, Maharaj said two reports existed and were obtained by "the intelligence section", presumably of the ANC, regarding the National Association of Democratic Lawyers (Nadel) and the Hank von Aandel Trust.

Maharaj said the reports showed there was a high-level source in Nadel who was being treated in a "particular and special way" and who was feeding information to the former National Intelligence Service (NIS).

The analysis concluded that "there was a reasonable basis to suspect Mr Bulelani Ngcuka", Maharaj said.

Documents were obtained from the then home affairs department which had to do with the application for the registration of a child born in Geneva. (Ngcuka lived in Geneva prior to his return to SA in the late 1980s).

"Through that application form one found Mr Ngcuka has three identity numbers. Clearly, one of those numbers became one to establish a cover identity for him," Maharaj concluded. He said on radio the report was surrendered to state departments after the 1994 elections.

The best independent person to adjudicate on this information is probably lawyer Dumisa Ntsebeza, who was both a founding member of Nadel and a commissioner at the Truth and Reconciliation Commission (TRC).

But Ntsebeza says the commission did not specifically investigate who spied for whom, something he now regrets.

The ANC presented to the TRC documentation it had on spies within its organisation, but it was focused on alleged spies who were executed at the Quattro training camp in Angola.

The ANC asked the TRC to keep this information secret, and it did so. Information on spies was provided by military intelligence. The commission met with NIS, but this was "a farce", Ntsebeza says, and no information of substance was passed on.

"The problem has always been the credibility of the sources," he says. Without the ability to create a controlled system to investigate the claims, the TRC considered the effort to be too difficult to tackle for the potential reward.

The atmosphere of the 1980s has be taken into account, where claims and counter-claims were often made on the flimsiest of evidence.

Perhaps the strongest argument against the spy allegation is the fact that Ngcuka held a series of senior positions in government.

He was selected by another prominent member of Nadel, Dullah Omar, who was then justice minister, to take up his position as head of the National Prosecuting Authority. Surely he would not have been appointed to these positions if doubts existed? Unfortunately, like everything else connected with spy allegations, this is not conclusive.

The NIA does not necessarily consider spying for the previous regime a bar to holding a post in the current government. It denies that the documentation said to be the basis of the allegation came from its records, although it might have come from records of its predecessors.

Another count against Maharaj's claim is that it is only being made public now. Ntsebeza wonders why the documents were not presented to the TRC with all the other ANC documents.

Scorpions spokesman Sipho Ngwema says the people who planted the information are desperate, have no integrity, no honour and no conscience.

So what is the truth? The truth is the facts in the circumstances. But what are the facts?

With acknowledgements to Tim Cohen and the Business Day.