By Jonah Fisher
BBC News, Johannesburg
Ms Pillay has set legal precedents on the treatment of genocide suspects
Navanethem Pillay, the United Nation's new commissioner for human rights, wants to be the "the champion of human rights in every part of the world".
Born in the South African city of Durban in 1941, this daughter of a bus driver was put through university thanks to donations from fellow members of the local Indian community.
Graduating with a law degree, Ms Pillay became the first woman to establish a legal practice in South Africa's Natal province.
"I had no choice," she told the BBC. "No law firm would employ me because they said they could not have white employees taking instructions from a coloured person."
Working as a lawyer under apartheid, Ms Pillay along with her black colleagues was not even allowed to enter a judge's chambers.
During those 28 years she is credited with exposing torture and the poor conditions of political detainees held by the apartheid police.
"I was representing men who were imprisoned on Robben Island along with Mandela," she said.
"They had no right to legal representation or even to know the rules of the prison. I was told by their wives just how bad the conditions were."
A successful appeal by Ms Pillay to the provincial court gave Nelson Mandela and his fellow inmates some very basic legal rights. Not surprisingly she soon found herself under constant surveillance from the security police.
"During her time in Natal she was a very courageous fighter for people at the wrong end of apartheid law," said Richard Goldstone, the South African former international war crimes prosecutor.
"Simply by making progress in the legal profession she succeeded in beating the odds."
Shortly after Nelson Mandela became South African president in 1994, he nominated Ms Pillay as the first non-white woman on the country's High Court.
But it was to be a short-lived appointment. She was soon recruited to sit as a judge on the International Criminal Tribunal for Rwanda.
While there she presided over landmark cases that established mass rape as a form of genocide.
Since 2003 she has been a judge at the International Criminal Court working on its appeals panel.
Navanethem Pillay's new role as United Nations Human Rights Commissioner will require a shift of focus. No longer will she be able to take a position of studied impartiality.
Back to advocacy
Campaigners expect the commissioner to be a powerful advocate for the world's oppressed, willing to be outspoken if necessary.
"Pillay will need to use her unique bully pulpit [public platform] to throw a spotlight on the world's worst violations, including Sudan's mass killing in Darfur, Burmese brutality, Chinese persecution, and Mugabe's destruction of Zimbabwe," said Hillel Neuer, executive director of UN Watch, an independent human rights group.
While understandably cautious on her first day in the job, Ms Pillay says she sees her new role as returning to that of being an advocate.
"This is the only office at the UN to be fiercely uncompromising and independent about human rights standards. The commissioner is the voice of the victim everywhere."
Ms Pillay replaces Canadian Louise Arbour in the role and earned the praise of UN Secretary General Ban Ki-moon, who said she has outstanding credentials for taking over the rapidly growing UN Human Rights Commission.
From humble beginnings, the commission now has a 1,000-strong staff based in Geneva and a budget of $120m (£60m).