The Constitutional Court said Zuma did not do enough to investigate allegations of misconduct levelled against Menzi Simelane before appointing him to the post.
Zuma tapped Simelane as National Director of Public Prosecutions in 2009 despite questions about his “credibility, integrity and conscientiousness,” Judge Zak Yacoob said.
The judge said that Zuma’s decision to ignore doubts about his candidate “coloured the rationality of the entire process, and thus rendered the ultimate decision irrational,” as well as “inconsistent with the Constitution and invalid.”
A 2007 presidential inquiry into a separate matter found Simelane an unreliable witness and dishonest, and Zuma disregarded another commission’s recommendation of disciplinary action against him.
Critics allege Simelane was selected to shield Zuma from corruption charges linked to a $5-billion arms deal, a case that has tainted South African politics for more than a decade.
Zuma and other government officials were accused of taking kick-backs from the purchase of jets, boats and other arms from five European firms, including BAE systems and French company Thales.
Charges against Zuma were ultimately withdrawn, but Zuma’s former financial adviser, Schabir Shaik, was sentenced to 15 years in prison for arranging bribes for Zuma, then deputy-president, in exchange for the contracts.
He was released on medical parole three years ago.