The leadership shambles at the National Prosecuting Authority has endured for so long cynics suggest it is being deliberately engineered. It is a saga that started more than a decade ago, with shameful allegations, spread by Jacob Zuma loyalists Mac Maharaj and Mo Shaik, that Bulelani Ngcuka, then national director of public prosecutions, was an apartheid spy.The ludicrous claims were discredited by the Hefer Commission, but the writing was on the wall for Ngcuka, whose crime was to publicly state that Zuma, then deputy president, had a ''prima facie'' case to answer in relation to graft allegations arising from the multibillion-rand arms deal, but that it was not winnable.It later emerged that acting NPA boss Mokotedi Mpshe had decided to withdraw more than 700 graft charges against Zuma in 2009 on the basis of intercepted telephone conversations between Ngcuka and Scorpions head Leonard McCarthy, which persuaded Mpshe that the state's case was tainted by political interference.After Zuma's disastrous appointment of Menzi Simelane as NPA head - Simelane was found by the Constitutional Court to be unfit to hold the office - the president seemed content to allow his close ally, the controversial Nomgcobo Jiba, to head the NPA on an acting basis for an inordinately long time.Finally, in 2013, Zuma appointed Mxolisi Nxasana as NPA head, only for it to emerge that Nxasana's security clearance had been denied as he had failed to disclose that he had been tried on a murder charge in 1985 and acquitted on the basis of self-defence.Then, early yesterday, the Presidency informed the Cassim inquiry, which was about to probe Nxasana's fitness to hold office, that its services were no longer needed.Now we will never know whether Zuma applied his mind properly in appointing Nxasana. One thing is clear: future NPA heads need to be appointed by parliament. Zuma has shown he cannot be entrusted with the task. ..