The father of Reeva Steenkamp has told a South African court that her fatal shooting by boyfriend Oscar Pistorius has "devastated" his family, and that he thinks about her constantly.
In a voice shaking with emotion, Barry Steenkamp revealed he has tried to imagine the horrific moment of his daughter's death, and said: "Oscar has to pay for what he did."
Mr Steenkamp added that he would like to talk to the former track star in private at a later stage.
He spoke at the sentencing hearing for Paralympic champion Pistorius, who was convicted of murdering his girlfriend at his home in 2013 in a case that transfixed the world.
The double-amputee, who also competed at the 2012 London Olympics, is currently under house arrest after initially serving one year of a five-year prison sentence for manslaughter for shooting Reeva Steenkamp on St Valentine's Day 2013 at his Pretoria house.
That conviction was overturned last year by an appeals court, which convicted Pistorius of the more serious charge of murder.
Judge Thokozile Masipa, who initially acquitted Pistorius of murder, will decide the new sentence.
The hearing is scheduled to run until Friday.
Pistorius shot model and reality TV star Reeva Steenkamp several times through a toilet door. He claimed in his trial that he thought his house had been broken into, and that he opened fire in the belief that an intruder was hiding behind the door.
South Africa has a minimum sentence of 15 years in prison for murder, although a judge can reduce that in some circumstances.
Barry Steenkamp gave testimony about the wrenching personal grief he suffered in the wake of his daughter's killing.
"She must have been in so much fear, pain," Mr Steenkamp said, his hands shaking at times. "That is what I think of all the time."
Under questioning from Nel, Mr Steenkamp urged Judge Masipa to allow the public to see the graphic photos of his daughter's wounds which were entered as evidence during Pistorius' trial, but not allowed to be shown to a wider audience.
Perhaps, Mr Steenkamp said, people who are "thinking of that type of deed" will hesitate before committing violent acts if they see the photos.
He said the death of Reeva contributed to his heart and other health problems, and that his wife June grieves just as much as he does despite what he called her "stone-faced" demeanour in public.
"I hear her at night," Mr Steenkamp said. "I hear her crying. I hear her talking to Reeva."
He said of his daughter's death: "It devastated us."
Sitting in the courtroom, Pistorius looked downward as Mr Steenkamp gave evidence. Afterwards, during an adjournment, the Olympic athlete sat hunched forward, apparently emotional, as his siblings, Carl and Aimee, sought to comfort him.
Earlier, a pastor and a woman whose son was born without legs testified for Pistorius' defence.
Pastor Marius Nel said he had been in contact with schools who want the double-amputee Olympian to help disadvantaged children with sports training.
The pastor also said he had visited Pistorius after he was jailed for the earlier manslaughter conviction and found him to be a "broken" man.
The evidence reflects an argument by defence lawyer Barry Roux that Pistorius should not go to jail because he can make a valuable contribution to society, and would face increasing mental deterioration if he returns to prison.
A nurse at the prison where Pistorius was jailed after his manslaughter conviction later testified for the prosecution about several alleged confrontations with Pistorius over medication and other issues.
In one episode, nurse Charlotte Mashabane said, Pistorius got angry because officials came to his cell for a routine check while he was sleeping.
Chief prosecutor Gerrie Nel said he would call his last witness on Wednesday for what he said would be "emotional" testimony.