Melbourne university student Henri van Breda made headlines around the world after his family was brutally murdered in their home in South Africa.

For three years, van Breda pleaded his innocence in the horrific crime, claiming a “tall, black man wearing a balaclava, gloves and dark clothes” broke into the house and began attacking his loved ones.

But last month a South African court sentenced van Breda to life behind bars for the murder of his mother, father and brother, and the attempted murder of his sister.

Judge Siraj Desai described the attacks as “savage and continuous” – but the world was left asking: why would a 20-year-old man want to attack his family and in such a brutal way?

Tonight in a world exclusive, 60 Minutes reporter Liz Hayes is given unprecedented access to the Henri van Breda murder case.

For the first time, van Breda’s girlfriend Danielle Janse van Rensburg breaks her silence, explaining to Hayes why she refuses to believe Henri is guilty.

“He told me everything,” van Rensburg said.

“He was very open. He was very honest.”

Van Breda is also backed by his aunt, Leenta Nell, who tells Hayes she has vowed to support her nephew – regardless of the guilty verdict.

“The Henri that I know – nothing in the 19 years that I knew him led me to think that there's a danger in Henri,” she told Hayes.

Detective Sergeant Marlon Appollis, a policeman for 14 years, also speaks to Hayes in tonight’s exclusive, revealing the van Breda case was one of the most confronting of his career.

“The moment you walk upstairs you see the blood spatter and stuff. Then you think to yourself, ‘What happened here, what went on?’”

Police video footage taken inside the van Breda family home reveals a devastating crime scene which Detective Appollis describes as particularly vicious.

Tonight for the first time, cameras will take viewers inside the crime scene to reveal the extraordinary trail of evidence that ultimately exposed van Breda’s guilt.

Despite the overwhelming evidence, van Breda told the court he was able to fight off the axe-wielding murderer and survived almost completely unscathed.

“He was a very lucky man with this axe-wielding attacker,” Cape Town prosecutor Susan Galloway said. It was Ms Galloway’s job to test the story as told by van Breda.

“One would like to think that there is something wrong with a person who does something like this,” Galloway said.

“We want to know that there's something wrong, because otherwise the possibility is there that each one of us are capable of something like this.”