Schabir Shaik has told the 10 judges of the constitutional court that he was convicted and jailed because he was the sacrificial lamb in the state's attempt to nab Jacob Zuma, the former deputy president.

"If anyone believes that my client was the ultimate fish that was sought to be landed [by the state], they obviously haven't been reading the newspapers," Martin Brassey SC, Shaik's advocate, told the court.

Shaik and the 10 companies in his Nkobi Group this week applied for leave to appeal against the supreme court of appeal's upholding of their conviction and sentences, and the related confiscation of their assets.

Shaik's claim that he was a scapegoat was not stated directly in the heads of argument because it is not usual legal practice to write "the state is a bully and made me the fall guy" or "I was a dummy run, a test specimen, used by the state to see whether it could later go after its real target, Jacob Zuma".

It is also difficult to make such an argument when you have been convicted in the high court of corruption and fraud (June 2005) and sentenced to 15 years' jail; the conviction and sentence have been upheld by a full bench of the supreme court of appeal (November 2006) and the state painstakingly demonstrated that you made more than 230 payments of various kinds to the man on his way to becoming, and who then became, the deputy president.

It is even more difficult to make such an argument now when you previously failed to raise it in the other two courts in which you have spent a great deal of time arguing your case.

Still, it was an ingenious argument that Brassey delivered, verbally, and he certainly won the attention of the court.

The nub of Shaik's argument was that he was unfairly tried, thus violating his constitutional rights, because he was charged with being in a conspiratorial relationship with Zuma and with Thint, the French arms dealer. And yet his co-conspirators were not charged alongside him.

This, Brassey argued, was unfair because no one could say what might have happened if Zuma had been charged alongside Shaik.

The issue of Zuma's exclusion from the trial became even more vexed, Brassey said, when one took into account the affidavit of Leonard McCarthy, the Scorpions boss, which was presented to the court during Zuma's aborted trial in September last year. This was because the affidavit allegedly made it clear that the Scorpions were merely waiting to see what happened to Shaik before proceeding against Zuma.

This brought one, Brassey said, back to the statement made in 2004 by Bulelani Ngcuka, then national director of public prosecutions. Ngcuka said then that there was a prima facie case against Zuma, but he would not be charged because it seemed to him that the case was not winnable.

Brassey argued that, in terms of the law, it was never a prosecutor's job to decide whether a case was winnable or not. He was supposed to prosecute without fear, favour or prejudice. It was a court's job to decide whether a case was won or lost.

This raised the question of why Zuma had not been charged alongside Shaik. The answer, Brassey suggested, was that the national director of public prosecutions had been anxious about taking the country's deputy president to court. In other words, he had been swayed by political considerations.

So the director had considered it wiser to charge Shaik alone - thus using him as a "dummy run" or "stalking horse". If the case against Shaik were successful, which it would prove to be, the state could then move against Zuma.

A number of judges asked Brassey what difference Zuma could have made because he obviously would not have said anything implicating himself. Brassey replied that speculation was irrelevant: either Shaik had been "irregularly" charged and thus given an unfair trial, or he had not.

But, pressed harder by the bench, Brassey said: "Can you imagine if Mr Zuma had been tried alongside Mr Shaik? … Can you imagine the quality of the trial and how different it would have been if Mr Zuma … had entered the box and said 'I want to tell you how it is between me and Shaik. Shaik is a friend of mine. You are asking me to tell you that Shaik tried to influence me in the execution of my decision-making powers. I want to tell you that he helped me, he helped me comrade-to-comrade, he helped me in the way a father helps a son [as far as finances are concerned]?"

Wim Trengove SC, for the state, said that Shaik's argument had to be turned down by the court because it was being raised for the first time when it could easily have been raised earlier.

He said that Shaik had been at liberty during his trial to call Zuma as a witness.

Trengove also argued that Ngcuka had genuinely been uncertain in 2004 whether Zuma could successfully be prosecuted - that it had not been a stratagem - and that Ngcuka's use of the word "winnable" had been used to explain the situation in layman's language during a press conference.

Trengove said that Shaik's petition was obviously an attempt by someone who had reached a dead end and was looking for yet another way to escape his punishment - and that the court should not allow him leave to appeal.

Shaik's application is for leave to appeal and so, it is understood, he will not need a majority of the judges to decide in his favour.

Legal sources said there was no specific written law on the subject, but the practice was that if a couple of the judges believed his appeal would "have a reasonable prospect of success", then the court would grant his application.

The court reserved judgment.

With acknowledgements to Jeremy Gordin and Sunday Independent.