JOHANNESBURG (Reuters) - More than any previous South African leader, President Jacob Zuma has personally experienced the country's justice system in action both before and after the end of apartheid.
Jailed for a decade on Robben Island Prison under apartheid, and then found not guilty on rape charges and escaping a corruption prosecution in post-apartheid South Africa, Zuma has had his fair share of days in court.
Now his critics accuse South Africa's fourth post-apartheid president of encroaching on the independence of the judiciary and appointing supporters to key posts as he fights to extend his presidency for another five years.
"We cannot allow the 'Zumafication' of South Africa's constitutionally independent justice system," opposition Democratic Alliance leader Helen Zille said this month.
Zuma's appointment of a relatively inexperienced judge as chief justice, the designation of his former trial adviser as the top corruption investigator and plans by the ruling ANC to review judgments of the Constitutional Court - South Africa's highest - reinforces a perception that the independent judiciary is under threat, analysts say.
The justice system has become a key battleground as the African National Congress is embroiled in serious infighting ahead of a crucial party conference to elect a new leader, and by implication South Africa's next president, a year from now.
"The judiciary is not so much in crisis as it is embattled," said Anne Fruhauf, Africa analyst at Eurasia group.
The independence of the judiciary is a cornerstone of South Africa's constitution and while courts have proven their autonomy in recent rulings, such as the Supreme Court of Appeals overturning Zuma's appointment of Menzi Simelane as head of the National Prosecuting Authority (NPA), there are fears it is now coming under attack.
"The judiciary has been involved in some bruising battles, both internal and external, over the past few years which has raised concerns over the relationship between the judiciary, the executive and the ruling party. There appear to be growing tensions over the balance of power between the executive and the judiciary," said Mike Davies, analyst at risk consultancy Maplecroft.
Zuma's appointment of supporters in key judicial roles is a cause for concern.
"It is true that Zuma seems to be surrounding himself with acolytes. This is quite apparent when you look at a string of personnel appointments and departures at the NPA (and) the intelligence services," Eurasia Group's Fruhauf said.
Zuma's appointment of former judge Willem Heath to head the Special Investigating Unit, one of the main anti-corruption agencies, was severely criticised by opposition parties.
Heath advised Zuma during a prolonged legal battle which culminated in graft charges against him being dropped in 2009 - clearing the way for him to become president.
Critics pointed to comments made by Heath in a newspaper interview after his appointment, in which he said former President Thabo Mbeki was behind the rape and corruption charges laid against Zuma.
This risked reviving memories of the bitter and damaging faction-fighting within the ANC that accompanied Mbeki's ousting by his own party and his replacement by Zuma as party leader in December 2007.
Zuma and the presidency distanced themselves from the comments by Heath, which are also the subject of a Justice Ministry inquiry.
But the opposition DA said Heath's comments showed he had aligned himself politically with Zuma.
"This raises serious questions as to whether he will be able to objectively and impartially conduct investigations into corruption at all levels of government," DA leader Zille said.
Corruption remains a blight in South Africa. Zuma fired two cabinet ministers and suspended the country's police chief in October to try to dispel criticism that he was soft on graft.
Still, corruption watchdog Transparency International ranked South Africa 64 out of 183 countries in its latest corruption perceptions index, which meant the country slipped 10 places from 2010.
Another battle that will most likely end up in court is one over a controversial secrecy bill, which the opposition, media and Zuma's ally the powerful COSATU trade union federation said they will fight, arguing it could allow corruption to remain unchecked.
The Protection of Information Bill passed by parliament last month allows any government agency to apply for classification of information that is "valuable" to the state and criminalises the possession and distribution of state secrets.
The secrecy bill has united opposition parties, but COSATU's outspoken criticism and lobbying against the bill may be the first concrete sign that the decades-old alliance between the ANC, labour and the South African Communist Party (SACP) may be on the rocks.
The ANC has long relied on its trade union ally to generate votes but fierce criticism by the SACP of COSATU over its stance on the bill showed the delicate state of the alliance.
"What all this points to is the steady crumbling of the ruling alliance, which is in a state of irretrievable conflict and confusion," independent political analyst Allister Sparks wrote in Business Day newspaper.
(Editing by Pascal Fletcher)