The court application by African National Congress President Jacob Zuma to have his prosecution declared invalid should "not be lightly entertained," Judge Chris Nicholson said as he started handing down judgment.

Zuma has requested the Pietermaritzburg High Court to declare the decision to prosecute him on fraud and corruption charges invalid, because the state did not consult him before going ahead with the prosecution.

Nicholson quoted lengthily from other judgments on similar cases, but said this case was different from those cited by State advocate Wim Trengove SC.

He traced the history of the investigation against Zuma back to 1999 when Independent Democrats leader Patricia de Lille tabled allegations of arms deal corruption in parliament, and the subsequent conviction of Zuma's financial adviser Schabir Shaik.

He said the country needed to rid itself of the "cancer that is devouring our body politic".

He also said there had been "dark mutterings" from Zuma that he would take people down with him like a blind Samson collapsing the temple onto himself.

Referring to the friends of the court's application for a commission of inquiry, he said he had no power to order this.

Only the president had these powers, Nicholson said, but did suggest a commission of inquiry into the arms deal.

Nicholson started delivering his judgment at 10am to a courtroom packed with the entire national executive committee of the ANC and other high-profile leaders.

The judgment was broadcast live on television and to the thousands of supporters gathered outside the court.

Zuma faces a charge each of racketeering and money laundering, two charges of corruption and 12 charges of fraud related to the multi-billion rand government arms deal.

He claims that the decision to prosecute him was a reversal of a decision taken by the former National Directorate of Public Prosecutions, Bulelani Ngcuka.

Ngcuka announced in August 2003 that the National Prosecuting Authority would not prosecute Zuma, because it did not believe that it had a "winnable case".

But after Shaik was found guilty of corruption in 2005, the state decided to charge Zuma after all.

The charges related to a government arms deal where Zuma allegedly used his influence to get lucrative arms contracts for Shaik's Nkobi Holdings, in return for payments totalling more than R4-million.

Nkobi Holdings and Thomson-CSF Holdings owned African Defence Systems, which won arms deal contracts.

The two South African subsidiaries of French arms manufacturer Thales International (formerly known as Thomson-CFS) - Thint Holdings (Southern Africa) Pty Ltd and Thint (Pty) Ltd - are co-accused and each face a charge of racketeering and two counts of corruption. Their case has been postponed until December 8.

Zuma further allegedly agreed to protect Thint Holdings (Thomson-CSF Holdings) from an investigation into alleged corruption in the arms deal, in return for a R500 000 a year bribe.

So far, Zuma has been mostly unsuccessful in attempts to block the state's case.

Earlier this year, a Constitutional Court challenge by Zuma failed. He contested the lawfulness of search and seizure operations by the state.

His case has had a ripple effect on politics in South Africa. Zuma is the front-runner to be elected as president next year and the ongoing uncertainty over his legal fate has cast a shadow over his election campaign.

Ngcuka, the first man to publicly mention Zuma's alleged involvement in the corruption charges, eventually resigned from office after being accused of being an apartheid spy.

Special Investigating Unit head Willem Heath, who was also investigating the arms deal, resigned after the justice minister at the time, Penuell Maduna, announced that he would disband the Heath unit.

Around the same time, Zuma told Parliament's standing committee on public accounts that there was no need to probe the arms deal.

After Ngcuka's departure, Vusi Pikoli was appointed as chief prosecutor but he has since been suspended by President Thabo Mbeki in a separate matter.

Media reports have also pulled Mbeki into allegations of bribery in the arms deal.

Since Zuma's election as ANC president at Polokwane last December, the ANC, which has repeatedly claimed that Zuma is being persecuted, has announced that it intends disbanding the Scorpions.

If convicted, Zuma faces a minimum of 15 years in jail.

Outside the court, a group of about 300 supporters tried to break a barricade set up directly opposite the court as the judgment boomed over a loudspeaker in the square.

The group started making a lot of noise, holding on to the gates and banging against them, trying to break through.

Police spokesperson Superintendent Muzi Mngomezulu said the police had everything under control and police marshalls were keeping an eye on the crowd. - Sapa