Durban - The decision not to prosecute deputy president Jacob Zuma was almost undoubtedly motivated by political or commercial interests, as there were no justifiable legal grounds for it, former judge Willem Heath said on Friday.

National director of public prosecutions Bulelani Ngcuka said last Saturday that while there was prima facie evidence of corruption against Zuma, the prospects of proving he had solicited bribes were slim.

Heath, who was kicked off the investigation into the R43 billion arms deal in late 2000, said prima facie evidence inherently had no loopholes.

"If there is no case against Zuma, there may be no case against Schabir Shaik either," said the former judge.

The charges against Shaik, who made his first court appearance this week, include using his friendship with Zuma to further his business interests through his company, Nkobi Holdings.

"To [convict] Shaik, the court would first have to prove Zuma's guilt as the two are inextricably linked," Heath said.

Heath said Shaik could have been charged to divert focus from the bad decision on Zuma.

"The case could drag on for months, by which time the heat would be off Zuma if Shaik was not convicted," he said.

Shaik said last week he was glad the matter had finally been brought to court. He said he was convinced the case had its roots in an international conspiracy to destabilise the government and "derail, or have a major influence, on the New Partnership for Africa's Development".

While Heath did not know of any occasion when Zuma might have been an obstacle to some international political or commercial interest, he said it was not impossible that international forces were trying to depose him.

"It is not unknown for people in one country to interfere in the running of another to achieve their own objectives," he said.

Heath last week announced his intention to canvas support for the establishment of an independent body to monitor corruption and manipulation in the criminal justice system.

"Of particular concern is the apparent insatiable appetite of the office of the director of public prosecutions to persecute high profile citizens and politicians whose commercial or political agendas are in opposition to certain people who can manipulate the course of justice," he said.

Democratic Alliance MP Sheila Camerer said an independent external forensic audit was the only proper way to probe links between the ANC and Shaik and Nkobi Holdings.

With acknowledgements to Margie Inggs and the Business Report.