Jacob Zuma will be in breach of his bail conditions, and risks jail, if he consults with former judge Willem Heath.

Heath, former head of the Special Investigating Unit (SIU) into the arms deal, was added to prosecutor Anton Steynberg's comprehensive list of state witnesses late on Wednesday.

When Steynberg handed in the initial list to the court, he said it was a condition of Zuma's bail that he would not be allowed to contact any of them.

Heath announced on Sunday that he had been briefed by an independent firm of Cape Town attorneys to serve as a consultant in Zuma's court battle against the National Prosecuting Authority.

Last night Heath told The Star he was not aware that his name had been added to the list of state witnesses.

He denounced the move as a ruse by the prosecution and said he would continue to consult with Zuma.

"I was briefed by Zuma before that list was drawn up. They're not entitled to stop Zuma from consulting me," he said.

"It's a ruse. When a witness is cited or subpoenaed and there's a fear that the accused will interfere or intimidate the witness, the court will order the accused not to contact the witness.

"None of these (concerns) was present in this instance."

Heath's surprise decision to assist Zuma triggered shock waves throughout the legal community.

Last night, a senior member of one of the country's law societies said: "There can be no doubt that Heath is out of order. There is a clear conflict of interests. If he is a witness for the state, he can't be advising the defence.

"If Zuma's bail conditions preclude him speaking to state witnesses, it doesn't matter who Heath was briefed by - the bail conditions are a total bar on Zuma speaking to Heath."

Zuma has provisionally been charged with two counts of corruption. It is believed that one will relate to an allegation that he had a "generally corrupt" relationship with his former financial adviser, Schabir Shaik.

The other is likely to relate to an alleged bribe agreement concluded between Shaik, Zuma and Alain Thetard, a former director of French arms company Thomson.

A senior serving judge contacted last night said Heath's decision had plunged the country into "virgin legal territory" in terms of the conflict-of-interest issue.

"It's a very strange decision. It's unprecedented because very few judges leave the bench and return to practise," he said.

"In Heath's case we have the situation of an investigating judge, which is even rarer, so we don't have that many precedents to guide us at all."

The judge said that because Heath was now a state witness, not even Zuma's attorneys or Heath's own instructing attorneys could speak to him for fear of interfering with the state's case.

"The whole bar on speaking to the state witnesses exists to prevent (anyone) from influencing the witnesses."

Independent Democrats leader Patricia de Lille last night expressed surprise at the timing of the release of the state's witness list. She had expected that everyone called in the Shaik case would be called again in the Zuma case.

"I only expected to hear sometime next year (of the list)."

De Lille also said she had been concerned at Heath's announcement that he would be assisting Zuma, given his previous role as head of the SIU.

"All of us who consulted with him when he was part of the SIU shared a lot of information, a lot of confidences.

"I thought (Heath's decision) was more of a commercial decision than anything else, but people make these kinds of choices nowadays.

"Heath said in newspapers that he wouldn't be representing Zuma, only giving him advice.

"The irony of it all... when he was at the SIU he worked for the state, now he works for the defence - but advocates can and do appear for the one side in one case and for the other side in other cases, so it's a commercial decision."

De Lille noted that Heath had indicated that he could be called as a state witness, and now that was the case.

"I can't see him going in contempt of court (and continuing to advise Zuma) for commercial reasons," she said. "Heath must keep to his word."

With acknowledgements to Estelle Ellis, Kevin Ritchie and The Star.