South African state lawyers have appealed against the dismissal of corruption charges against African National Congress leader Jacob Zuma.
The charges were rejected on a technicality in September, sparking a political row, which led to President Thabo Mbeki leaving office.
The judge accused the state prosecutors of interfering in the case for political reasons.
Mr Zuma is favourite to win general elections due next year.
Security is reported to be tight outside the Supreme Court of Appeals in the central city of Bloemfontein
Mr Zuma was surrounded by bodyguards when he arrived at the court where a large number of journalists were gathered, the South African Press Association reports.
Mr Zuma's supporters started arriving in buses shortly after the legal teams, and have been singing their support for the ANC leader outside the courthouse.
Right to defence
Mr Mbeki denied any political interference but lost an appeal against that part of the judgement earlier this month.
But he is expected to argue in court that he should be allowed to be party to the case.
He argues it was unfair of Judge Chris Nicholson to pass judgement on his government's actions without giving him the right to defend himself.
Mr Mbeki lost a bitter contest for the leadership of the governing ANC to Mr Zuma last year.
Mr Zuma has always denied charges of graft, money-laundering and racketeering, stemming from a controversial $5bn 1999 arms deal.
Judge Nicholson stressed that his September ruling had no bearing on the guilt or otherwise of Mr Zuma. But dismissing the charges meant that Mr Zuma would be free to lead the ANC in the elections.