The Supreme Court of Appeal (SCA) in Bloemfontein is expected to hand down judgment in the appeal by President Jacob Zuma and the National Prosecuting Authority (NPA) in the spy tapes saga.

The ruling will be delivered on Friday at 09:30 in court A.

Last month the president and the NPA conceded that former NPA head Mokotedi Mpshe's decision not to prosecute Zuma on corruption charges was irrational.

Advocate Kemp J Kemp, SC, for Zuma, told the full bench of justices that he believed that the NPA had erred in their decision.

"Lets take it a step further - in other words, they made an irrational decision?" Justice Azhar Cachalia quizzed Kemp.

"That is then correct, yes," Kemp replied at the time.

Zuma and the NPA have approached the SCA in Bloemfontein, seeking leave to appeal the 2016 decision by the North Gauteng High Court in Pretoria on the "spy tapes" saga.

Kemp said that if the SCA finds that Mpshe did not make a rational decision, then someone would have to make a rational decision on that basis.

The long-standing matter was brought by the Democratic Alliance.

Advocate Hilton Epstein, SC, for the NPA, faced tough questions at the time from the visibly unimpressed judges, who pressed him on who had decided on whether Zuma should be prosecuted or not.