The question Oscar Pistorius REFUSED to answer: How private conversation between Reeva Steenkamp's father and Paralympian killer can finally be revealed... as he's freed after 10 years

Reeva Steenkamp's father went to his grave convinced that Oscar Pistorius was guilty of shooting his daughter dead on purpose - because he was unable to swear a personal oath that he was innocent.

Mr Barry Steenkamp, who passed away in September, posed a simple question he was convinced would finally force the truth from the Paralympian who shot her dead on Valentine's Day 2013 but always protested his innocence, MailOnline has learned.

Pistorius, 37, who was granted his freedom yesterday after serving more than half of his 13-year sentence, was confronted by Mr Steenkamp who begged him to come clean during a private meeting took place in June last year.

Pistorius agreed to meet the Steenkamps in prison, as part of South Africa's victim-offender dialogue programme. The killer had to convince Mr Steenkamp he acknowledged the harm he had caused.

Pistorius was flown from Pretoria to a detention centre close to their Port Elizabeth home. Reeva's mother decided she did not feel able to meet him due to the mental torture she felt he had inflicted on her and the anger she still carried. But her husband wanted to finally get to the truth.

Full details of the conversation have remained private until now at Mr Steenkamp's request.

Since the murder of Reeva, Pistorius had been strongly backed by his tight-knit family, particularly his brother Carl and London-based sister Aimée, who have all supported his claims that he shot Reeva by accident in the belief that an intruder had entered his home while the couple slept.

Mr Steenkamp, who was 80, strongly believed the shooting was calculated because his daughter wanted to end the relationship, but he listened intently to Pistorius's pleas of innocence as the Blade Runner broke down and wept.

But Mr Steenkamp revealed: 'I spoke to him and I told him he was lying.

'I looked directly at him, but he could not look me in the eye.

'I said 'you have got a brother and a sister. On their life…are you telling me the truth'?

Pistorious was unable to answer, Mr Steenkamp said: 'He just put his head down ...and I left.'

Mr Steenkamp who longed for ten years to hear Pistorius at last reveal he had murder on his mind when he opened fire on Reeva, said his silence at that pivotal moment spoke volumes about his guilt.

'If he had admitted it, he would have felt different as well. That part of her would have gone. He will have to live with his evil secret.'

He said he never once felt like punching the man who took the life of his only daughter.

'It would not have been worth it. I would have rather got into the ring with Tyson Fury…I would have felt better.'

Mr Steenkamp, who was in poor health and had suffered a stroke, told Mail Online that the moment of the shooting as described by Pistorius was 'utter rubbish.'

He said: 'I believe that there was something prior to that. There must have been one hell of an argument.

'Her clothes were thrown out of the window and found outside. She was trying to leave, but she couldn't jump out of the window.'

He and Mrs Steenkamp said the height of the balcony to the ground at Pistorius' Pretoria home prevented Reeva from escaping and 'she would have been left in a wheelchair.'

Mrs Steenkamp added: 'Reeva must have thought 'can I do that?', but at least if she had, she would have been alive.'

Mrs Steenkamp said despite being a free man, Pistorius would be haunted by Reeva for the rest of his life.

She added: 'He will see her face whenever he closes his eyes. Apparently, he hardly sleeps without medication because he obviously sees her face and that is going to be there forever.'

Mrs Steenkamp said one of her daughter's two cell phones was still missing and both were with her on the night of her slaughter. Her handbag had also still not been recovered.

'There is a whole lot more to the story' she added.

In her impact statement to Pistorius' parole hearing, she said she believed the athlete had taken not only the life of her daughter, but her husband as well.

'I have no doubt that Barry died of a broken heart. No parent should have to bury a child and most certainly not in the circumstances that prevailed in the demise of Reeva.

'Following Reeva's death, Barry and I, both devastated, tried with whatever emotional reserves that remained to take care and support one another.

'My dear Barry left this world utterly devastated by the thought that he had failed to protect his daughter and therefore in his role as father, as he perceived it.

'The pain caused by the dastardly murder of Reeva, did not only include emotional trauma. It also included trauma that manifested physically as became evident in the accelerated deterioration in health for both Barry and myself.'

A United Nations backed campaign against gender based violence, backed by Mrs Steenkamp, begins today and the Pistorius murder of Reeva is expected to be heavily used to back the 16 day project in South Africa by protesters.

The 16 Days of Activism against Gender-Based Violence is an annual international campaign which begins today to mark The International Day for the Elimination of Violence against Women, and it will continue until 10 December, Human Rights Day.

The campaign was started by activists at the inauguration of the Women's Global Leadership Institute in 1991. It is used as an organising strategy by individuals and organizations around the world to call for the prevention and elimination of violence against women and girls.