Reeva Steenkamp’s father broke down in the witness box as he told Oscar Pistorius’s sentencing hearing how he and his wife have struggled to cope since his daughter’s murder.

The former Paralympic and Olympic athlete is due to be sentenced for the murder of his girlfriend after his initial manslaughter conviction – for which he served 10 months of a five-year sentence – was upgraded to murder upon appeal.

Her father, Barry Steenkamp, said Pistorius must “pay” for his actions – before speaking about the emotional impact of his daughter's death.

“Morning, noon, at night, early hours of the morning. I think about her all the time,” he said, shaking and holding back tears as he did so.

He said he thought “there had been an argument” between his daughter and Pistorius on the night she was killed, but was stopped from elaborating further for legal reasons by State Prosecutor Gerrie Nel.

“People say it takes you two years, three years and you start feeling a bit better about the whole thing,” he said. “But every day of my life is the same. I talk to her. If I see a feather, or something like that. Reeva is with me all the time, yes.”

Mr Steenkamp, 73, said his daughter’s death had “changed him completely”.

“I wouldn’t say I’m a recluse, but I can’t really mix with people anymore. I sit on my veranda, at two, three o’clock in the morning. I smoke my cigarettes and drink my coffee.

“I get messages virtually every day on Facebook, from people who support us. Photographs of Reeva. I must have a couple of hundred of them, which I go through every day.”

Oscar Pistorius: Career in pictures Show all 34 1 /34 Oscar Pistorius: Career in pictures Oscar Pistorius: Career in pictures Oscar Pistorius in Greece Oscar Pistorius wins the 200m T44 for Men during the Athens 2004 Paralympic Games at the Olympic Stadium in Athens, 2004 Oscar Pistorius: Career in pictures Oscar Pistorius in Greece Oscar Pistorius at the Olympic Stadium in Athens, 2004 Oscar Pistorius: Career in pictures Oscar Pistorius in Manchester Oscar Pistorius celebrates winning his second gold medal during the VISA Paralympic World Cup Athletics at the Sport City Stadium in Manchester, 2006 Oscar Pistorius: Career in pictures Oscar Pistorius in Manchester Oscar Pistorius shows his gold medal after winning the T44 200 m for men at the Visa Paralympic world cup at the Manchester Regional Arena, 2007 Oscar Pistorius: Career in pictures Oscar Pistorius competes in race Oscar Pistorius competing in the men's 400m race B, 2007 Oscar Pistorius: Career in pictures Oscar Pistorius in Rome Oscar Pistorius settles in the blocks before winning the Mens 400m 'B' race during the IAAF Golden Gala at The Olympic Stadium in Rome, 2007 Oscar Pistorius: Career in pictures Oscar Pistorius in Rome Oscar Pistorius poses during the broadcast 'Piazza grande' on Italian TV state channel 'Rai 1' in Rome, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in St.Petersburg (L to R) Bryan Habana, Cuba Gooding Jr and Oscar Pistorius during the Laureus welcome reception at Gimnazya in St.Petersburg, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius arrives at the Court of Arbitration for Sport (CAS) in Lausanne Oscar Pistorius arrives at the Court of Arbitration for Sport (CAS) in Lausanne to appeal his case on the second day of his hearing as he was told by the International Association of Athletics Federations (IAAF) that he could not compete in their events because the artificial legs he uses gives him an unfair advantage, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius runs during a training session Oscar Pistorius runs during a training session on the track of Emmeloord, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in Germany Oscar Pistorius compete during the 400 meter race at the German disabled athletics championships in Berlin, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in Italy Oscar Pistorius of South Africa relaxes prior to the 400m race in his quest to make the Olympic qualifying time of 45.55 during the Notturna di Milano International Athletics Meeting at the Arena Gianni Brera in Milan, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in China Oscar Pistorius speaks at a press conference for the 2008 Beijing Paralympic Games in Beijing, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in China Oscar Pistorius of South Africa celebrates after winning the gold medal in the Men's 100m T44 Final Athletics event at the National Stadium during day three of the 2008 Paralympic Games in Beijing, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius in China Oscar Pistorious (L) leads Heros Marai (C) of Italy and Christoph Bausch (R) of Switzerland in the heats of the men's 100 metre T44 classification race at the 2008 Beijing Paralympic Games in Beijing, 2008 Oscar Pistorius: Career in pictures Oscar Pistorius and Nelson Mandela in South Africa Oscar Pistorius and former South African President, Nelson Mandela in South Africa, 2009 Oscar Pistorius: Career in pictures Oscar Pistorius in Norway Oscar Pistorius looks on prior to the 400m B-final during the IAAF Golden League Bislett Games in Oslo, 2009 Oscar Pistorius: Career in pictures Oscar Pistorius in London Oscar Pistorius reacts after winning the men's 400 metres T44 final race with a new world record time of 47.04 sec during the Diamond League athletics meeting at Crystal Palace in London, 2010 Oscar Pistorius: Career in pictures Oscar Pistorius in New Zealand Oscar Pistorius of South Africa celebrates receiving his gold medal after winning the Men's 200m T44 final during day three of the IPC Athletics Championships at QE II Park in Christchurch, New Zealand, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in New Zealand (L-R) Arnu Fourie, Henry Roos, Oscar Pistorius and Mike Samkelo Radebe of South Africa celebrate after winning the Men's 4x100m Relay T42-46 final during day eight of the IPC Athletics Championships at QE II Park in Christchurch, New Zealand, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in New Zealand Oscar Pistorius of South Africa poses with his medals during day eight of the IPC Athletics Championships at QE II Park in Christchurch, New Zealand, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in South Africa Oscar Pistorius in action during the 400m during day 5 of The Nedbank National Championships for the Physically Disabled from Olympia Park Stadium in Rustenburg, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in Czech Republic Oscar Pistorius warms up before the men's 400m event at the Zlata Tretra (Golden Spike) athletics meeting in the eastern Czech city of Ostrava, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in New York Oscar Pistorius attends the Eva Mendes launch of her new campaign for Angel by Thierry Mugler at IAC Building in New York, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in South Korea Oscar Pistorius of South Africa speaks with Olympic gold medalist Michael Johnson of the United States during a media gathering at the Novatel Hotel prior to the 13th IAAF World Athletics Championships Daegu 2011 in Daegu, South Korea, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in South Korea Oscar Pistorius prepares to settle into the blocks to compete in the men's 400 metres heats at the International Association of Athletics Federations (IAAF) World Championships in Daegu, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in London South African sprint runner known as 'Blade Runner' Oscar Pistorius (C) poses for photographers with Paralympians ahead of the international Paralympic Day in central London, 2011 Oscar Pistorius: Career in pictures Oscar Pistorius in London Oscar Pistorius poses in the press room with his Laureus World Sportsperson of the Year with a Disability trophy at the 2012 Laureus World Sports Awards at Queen Elizabeth II Conference Centre in London, 2012 Oscar Pistorius: Career in pictures Oscar Pistorius in London Oscar Pistorius of South Africa competes in the Men's 400m Round 1 heat on Day 8 of the 2012 London Olympic Games at the Olympic Stadium in London, 2012 Oscar Pistorius: Career in pictures Oscar Pistorius receives his honorary doctorate Oscar Pistorius holds his scroll after receiving his honorary doctorate from Strathclyde University in the Barony Hall in Glasgow, 2012 Oscar Pistorius: Career in pictures Oscar Pistorius with his girlfriend Oscar Pistorius posing next to his girlfriend Reeva Steenkamp at Melrose Arch in Johannesburg, 2013 Oscar Pistorius: Career in pictures Oscar Pistorius in court Oscar Pistorius hides his face in his hands in the court room during his hearing on charge of murdering his model girlfriend Reeva Steenkamp at the Magistrate Court in Pretoria, 2013 Oscar Pistorius: Career in pictures Oscar Pistorius in court Oscar Pistorius stands in the Magistrate Court in Pretoria after appearing for the first time since being freed on bail over the Valentine's Day killing of his model girlfriend, 2013 Oscar Pistorius: Career in pictures Oscar Pistorius in court Oscar Pistorius appeared on charges of murdering his model girlfriend Reeva Steenkamp, 2013

He said the Christian approach his wife, June, had taken in response to their daughter's murder did not absolve Pistorius of blame.

"She feels it’s right in her heart to forgive Oscar," he said. "It still does not exonerate you for the crime that you committed. He must still understand that he has to pay for that.

“June has forgiven him so that she can carry on with her life. But I feel the same, that Oscar has to pay for what he did. He has to pay for it.

“That is up to the court. And we will go by the decision that the court hands down to Oscar. But he has to pay from his crime.

“I don’t want to say that he has to go to the maximum… But he has to pay for it.”

As Pistorius, 29, looked on almost expressionless, Mr Steenkamp told the court of what happened on the night of the murder, when he received a phone call from his wife.

“She said, come home immediately. Come home. I realised Reeva’s name was there. That’s when I started the panic. I realised more and more that Reeva has been killed. It’s like it happened yesterday. That’s how I first heard about it.

“I don’t wish that on any human being,” he said. “Finding out what happened. It devastated us. I ended up having a stroke. And now so many things since then have happened where I’ve gone to doctors, and to surgeons, which I still have to go into, for my heart, and everything like that. I don’t wish that on anybody in this whole world.”

He said press reports had said he and his wife were close to bankruptcy, which their landlady saw and served them notice on their home and they were forced to move out.

He told the court he thinks “all the time” of “what she must have gone through in those split seconds. She must have been in so much fear and pain. That is what I think of all the time.”

Mr Steenkamp, who suffers from diabetes, said at time he had used “his needles to shove into my legs and into my arms and see if I could feel the same pain, but no.”

He also revealed he was “disgusted” when it came up in court that he and his wife had agreed, on the advice of his lawyers, to receive money from the Pistorius family.

Oscar Pistorius as he awaited trail at Pretoria Magistrates Court in 2013 ( Reuters) (REUTERS/Siphiwe Sibeko)

“It was discussed between the defence lawyers and our lawyers. They arranged that amongst themselves,” he said.

“We didn’t like the idea but we were in dire straits at the time. Barry, don’t worry, this will be private and confidential. I said I’ll leave it up to you to do what you must do for us. I heard it was Mr Barry Roux who requested it stayed private and confidential.

“I was disgusted when it came out that something like that could have been brought up. And immediately when we were offered 360,000 rand, we immediately declined it. We said we don’t want it. It makes no difference. It’s my daughter that’s gone. It’s not the money.

He also said he had seen “only one photo” of Reeva’s murdered body, the one that was produced in court when Mr Steenkamp was present two years ago, but that he wanted “the world to see” the others, as a warning to anyone thinking of using firearms.

He also indicated he would be willing to meet Oscar Pistorius and “talk to him” but “not now, not yet".