Born in the Orlando West district of Soweto, she lived not far from Nelson and Winnie Mandela.
One of 10 children - five of whom died in childhood, and one of whom was stabbed to death in his 20s - Masipa's early years were spent in a two-bedroom house, where she'd be put on lookout duty to watch for police as her grandparents brewed homemade beer.
But she was a studious young girl who, by her own admission, "wasn't a great socialiser". She added: "I would be buried in my books."
Inspired by her mother, a teacher, she went into social work - but was frustrated that her lack of financial support meant going to university was impossible.
To fund her further education she took on additional work as a clerk, a messenger and a tea girl until, finally, she could attend university and study social work - graduating in 1974.
She was appointed as crime correspondent for the newspaper World, where she reported on the increasingly violent struggle against apartheid - including the murder of activist Steve Biko in 1977.
The newspaper was shut down that year, but Masipa went on to become women's editor of the Post newspaper, where she wrote about schools, education and labour conditions for domestic workers - often to the anger of the authorities.
Aged 29 she marched in support of press freedom and found herself in prison, sleeping for one night on the concrete floor and disobeying orders to clean the filthy, overflowing lavatories which had been left for them inside their cell.
It was an experience which many say helped to cement her passion for human rights, and her hatred of injustice.
In 1980, by then married to a tax consultant and with two small children, she began to study law - a course which would take her 10 years, funded by her fulltime job as a journalist.
By the time she qualified, Gerrie Nel - who led the prosecution in the Pistorius trial - already had six years' experience, despite being about a decade younger.
But her relatively late arrival did not prevent her from becoming, in 1998, only the second black woman to be appointed a judge.
And she has earned a reputation for being tough, intelligent and unafraid of controversy.
Freddy Mashamba, a police inspector, was handed a life sentence in prison for shooting and killing his wife in 2009.
A year ago she sentenced a serial rapist to 252 years in prison, saying: "The worst in my view is that he attacked and raped the victims in their own homes where they thought they were safe." During the Pistorius trial she kept her thoughts on his actions to herself - sharing them with no one in the court, and being driven alone from her Midrand house to the courtroom in Pretoria every day.
With her heavy caseload, it was her husband who cooked food for the family.
The courts service insists her allocation to the trial, during which she was assisted by two assessors, was a routine rotation, and had nothing to do with her past activism or present case expertise.
But it has not stopped her story being seized upon by observers of the case - and held up as a mirror into the soul of modern South Africa.
The fate of a wealthy Afrikaans superstar lay in the hands of a township-born black woman - but one who believes in justice, whatever that may be.
