There was what the academics would call a seminal moment this week at the Hefer Commission in Bloemfontein, a moment that occurred during the cross-examination of Vusi Mona, the former editor of City Press, by Kessie Naidu, commission evidence leader.

At first, when cross-examination began, it was clear that Mona did not realise what was coming his way.

But, as Naidu started hammering at him, beginning by cornering Mona into admitting that he was giving "false" evidence, and as retired Judge Joos Hefer, the commission chairperson, asked Mona whether he had the faintest idea of what "the whole truth" was, Mona's smile was expunged, his face clouded, he squirmed in his chair, and he hung his head. Mona's expression - the fear, the hang-dog look, the swivelling of his eyes in search of a non-existent way out - felt like a harsh and uncomfortable flashback to scenes from this country's past.

It could be argued that this interpretation is unfair, that Mona's expression was that of any cornered person anywhere, any time. Yet there was something about his hunted, rabbit-in the-headlights look that brought back memories of the South African past. Whether people like it or not, the past itself has sat in at the commission, an invisible observer that simultaneously takes up no space and yet a great deal of space.

After all, the commission's mandate is to examine whether Bulelani Ngcuka, the national director of public prosecutions, was an apartheid-era spy who had "abused" his present position as a result.

In other words, at the heart of the commission is the question : could the present national director of public prosecutions have been the worst kind of human being that anyone could have been during the struggle - an informer, impimpi, sellout? Most of the evidence so far has resolved around aspects of the African National Congress struggle against the former regime, and vice-versa - the intelligence war, detentions, treason trials and torture.

And the security policemen and spies of the past have also appeared at the commission, albeit not in person. Among these have been Karl Edwards, the former security police handler of Vanessa Brereton, the self-confessed informer RS452, and Gideon Nieuwoudt, the former policeman implicated in the death of Steve Biko and the gruesome killings of numerous others, and already named as a perjurer.

It may well have been Mona's dismissive remark, in earlier cross-examination, that he thought it was "okay" to trust what Niewoudt said about Ngcuka, even though he knew what Nieuwoudt had allegedly done, that ignited the rage of Naidu.

But of course this is 2003 and Mona was appearing voluntarily before the commission.

What was significant about Mona is that it was the City Press newspaper, of which he was the editor, that first carried the story that Ngcuka had been investigated as a spy.

More importantly, it was Mona who had complained to the public protector about a September off-the-record briefing that Ngcuka held with six newspaper editors.

According to Mona, Ngcuka had at this briefing abused his position in a particularly unpleasant way by slandering a number of people, including Mac Maharaj, the former transport minister, and by making a racist remark about Indians.

His evidence thus went to the heart of whether Ngcuka has abused his position as national director of public prosecutions, and this was why Naidu and everyone else were intent on testing him by fire.

He also did not win any friends on the commission by repeatedly and self-righteously stating that his only reason for being at the commission, for having written to the public protector and for having betrayed the confidentiality of the off-the-record briefing, was his belief that Ngcuka had violated the constitutional rights of those he allegedly defamed.

Someone, perhaps his attorney, who was unfortunately absent for parts of his cross-examination, ought to have told Mona that people like Hefer, Naidu, senior counsel Norman Arendse, appearing for Penuell Maduna, the justice minister, and senior counsel Marumo Moerane, appearing for Ngcuka, have been around the block to many times to buy without examination of "fanciful story" (as Naidu called another part of Mona's evidence)- especially as this claim was coming from someone who had left his newspaper following allegations of impropriety.

For roughly eight hours, Mona was set up by Arendse. Doggedly, patiently, Arendse pushed Mona into putting as much as possible on the record.

Then, after lunch on Thursday, Naidu, using Mona's on-the-record testimony as a blueprint, proceeded to discredit the former editor and to suggest that Mona's true motives for divulging the off-the-record briefing had more to do with concerns that he was himself being investigated by the Scorpions and by the pressures of third parties.

Mona was forced to concede that he had been reckless, had given incorrect evidence to the commission, had on important occasions "not applied his mind" and was overall a "disgrace to his profession", as Moerane later said to him.

It was not pretty, and one may be forgiven for wondering whether the old South Africa was sniggering in the back row of the commission and sarcastically asking just how much the new South Africa has changed, at least in the hearts of people.

With acknowledgements to Jeremy Gordin and the Sunday Independent.