The Scorpion raids on former Deputy President Jacob Zuma's lawyers and the Union Buildings was "highly unusual" but not illegal, says a law professor from the University of KwaZulu-Natal.

"However, in executing the search, parts of their conduct may be challenged," said Professor Robin Palmer.

The Scorpions swooped on the homes and offices on Thursday of several people linked to Zuma, who goes on trial for corruption in October.

Palmer said: "What this means is that nobody is above the law and the Union buildings do not have special status."

However, he said the question which should be asked was whether the Scorpions investigated everyone "without fear or favour" or whether there was "selective prosecution".

In the context of many scandals in South Africa, the Zuma case was "small fry", but big in the sense that he was the deputy president.

"But what about the R11-million rand clearly misappropriated in the 'Oilgate' scandal? That is clear corruption on the face of it."

Palmer's comments came as Zuma's personal lawyer Julie Mohamed on Friday morning waited to receive the affidavit upon which the search warrant was obtained giving the Scorpions access to her home and office in Johannesburg.

"What drastic information did they require to justify the breach of attorney-client privilege? My other client's files, who have nothing to do with Zuma, were also perused page by page and attached," Mahomed said.

"I'm simply outraged."

After obtaining all the necessary information she would decide on what action to take.

Edward Ngubane, president of the Black Lawyers Association, said the raids on attorneys offices were "of grave concern".

"The general rule is that information between a client and attorney is privileged in so far as it relates to advice an attorney gives to a client, or advice sought by a client from his attorney in anticipation of impending legal action," Ngubane said.

However, he said searches were allowed if the attorney was suspected of a crime.

"Without the full facts it is difficult to criticise or laud it, but it is a matter of grave concern."

Rhodes University dean of law Rob Midgley said that under the Criminal Procedure Act and the Rules of Evidence, investigators are allowed to continue gathering evidence after charges are laid and right through the trial.

In response to opinion that the raids should have been conducted before Zuma was charged, Midgley explained that the Directorate of Public Prosecutions could charge someone as soon as it had sufficient evidence to do so, and then continue investigating.

"You don't have to stop investigating as soon as you have charged somebody," Midgley said.

As long as the correct legal procedures were followed - which included obtaining search and seizure warrants - investigations could continue and evidence could be presented until the prosecution closed its case in court.

There was also a procedure for the introduction of new evidence even after this point, before the verdict was given.

Prosecutors could apply for permission to reopen the case and present new evidence and this would be considered by the presiding officer, Midgley said.

"The final cut-off point for producing new evidence is when the verdict is reached."

He said that a person whose sentence was on appeal was also allowed to be searched if the search related to another case - in this case, the Zuma investigation.

"His case (Schabir Shaik) is separate and it follows its own course. You can't add new evidence to his case," Midgley said.

Shaik was convicted on two counts of corruption and one of fraud earlier this year, all relating to Zuma. His brother Mo Shaik said the functions and transformation of the National Prosecuting Authority, which controls the Scorpions who carried out the raids, should be debated.

"Has the FBI (US Federal Bureau of Investigation) ever raided the White House or the police number 10 Downing Street (home of the British prime minister)?" he asked.

NPA spokesperson Makhosini Nkosi said there were no further raids on Friday and would not comment further on the matter.

With acknowledgements to Sapa and Independent Online.