Mo Shaik on Thursday told the Hefer Commission of Inquiry, which is investigating spy claims involving National Director of Public Prosecutions Bulelani Ngcuka, that he would be happy to concede he had been wrong about Ngcuka, as long as he could be shown to be wrong.

The former ANC intelligence head told the commission on Thursday that he had he found it "incredibly odd" that Ngcuka had received his passport so quickly in the 1980s.

"That didn't happen in South Africa … that you apply for a passport today and you get it tomorrow."

Judge Joos Hefer asked Shaik: "How would you rate the chances … probably, or possibly, that Mr Ngcuka was one [a spy]?"

"From the information at my disposal, my experience, with what I know, I cannot come to the conclusion that he was not a spy," Shaik answered.

"That's all very negative," said Hefer, to which Shaik replied that "if you cannot prove the null hypothesis, then the corollary applies".

Shaik said he that "feels" for Hefer, in that he would have a very difficult task in ascertaining whether Ngcuka was a spy.

Shaik said that sometimes it may take up to 20 years for someone to be identified as a spy.

Evidence leader Kessie Naidu put it to Shaik that reports that Nguka had been recruited as a spy "were not much better than gossip".

"Do you have any documents upon which this analysis was based? All you rely on is intelligence information."

Naidu then pressed Shaik to name the person who fingered Ngcuka. Shaik refused to disclose the name, but said he had been given the information in November 2002 by a former brigadier general.

Naidu contended there was no way of "testing this hearsay evidence".

Explaining how he had reconstructed his report (which Sunday Times reporter Ranjeni Munusamy apparently used as the basis for her article about the spy claims against Ngcuka), Shaik said: "Having left [the] intelligence [service], I reobtained my databases and went back to my information … After a discussion with a senior police officer, I reconstructed my analysis and felt compelled to make a senior officer of the intelligence community aware of it.

Shaik appeared to be on the verge of tears, and after a long pause, said that in 1989 or 1990, information had been in his possession and that he had been slow to react to that information.

"As a consequence, people died."

Shaik again seemed to lose control when his cross-examination appeared to move towards his own interrogation and torture during the liberation struggle.

He threatened to get up and leave the witness box if Naidu reminded him of his "humiliation" in this regard.

"Torture is a humiliating experience, of which you have no experience. You respect it … or I'll leave now, shouted Shaik.

With acknowledgements to the staff reporter, Sapa and the Mail&Guardian.