A cousin of Reeva Steenkamp, who was shot dead by South African athlete Oscar Pistorius, said Thursday that he should "pay for what he has done" with a prison sentence, as she testified at his sentencing hearing.

Kim Martin, the first witness called by state Prosecutor Gerrie Nel, also dismissed suggestions that the double amputee should serve a sentence of house arrest or community service, saying that would not "fit the crime."

"This is not easy for me. I really believe the accused, Mr. Pistorius, needs to pay for what he has done," she said, sounding choked with emotion.

"My family are not people who are seeking revenge. We just feel that to take someone's life, to shoot somebody behind a door that is unarmed, that is harmless, needs sufficient punishment."

Martin, testifying for a second day, told the court that initially, she was worried about prison conditions for Pistorius, but when she realized that he'd be treated humanely, she felt he should receive jail time.

"Everybody has suffered here, and I think we need to give a message to society that you cannot do this and get away with it," she said.

Pistorius' sentence -- custodial or not -- will be decided by Judge Thokozile Masipa, who also presided over his trial.

The Olympian was cleared of murder last month but found guilty of culpable homicide, or negligently killing Steenkamp, when he fired four shots through a toilet door in his home. He said he believed there was an intruder behind the door.

Martin said she was "very fearful of the accused" and had tried to put him out of her mind. "We even made a point of not mentioning his name in our house because I didn't want to spend any energy thinking about him," she said.

Defense attorney Barry Roux asked Thursday if Martin was aware that Pistorius had written letters to Steenkamp's family but under advice from his lawyers hadn't given them to the family.

He said that Pistorius wants privately to apologize to the family.

Martin is the only member of Reeva Steenkamp's family to have testified before the court, though the model's parents, Barry and June Steenkamp, have been present for proceedings.

On Wednesday, Martin said that the health of Reeva's father, Barry Steenkamp, has suffered as a result of his daughter's death and that he had a couple of strokes.

"It's ruined our whole family. It's ruined Barry and June. Reeva was everything to them," she said.

Acting National Commissioner of Correctional Services Zach Modise told the court Thursday that the system would be able to meet Pistorius' needs as a disabled prisoner.

Modise said that South Africa's prisons are used to taking in all kinds of prisoners, including juveniles and the elderly, and that there are facilities to deal with every kind of inmate.

The prison system deals with 128 disabled inmates on a daily basis, he said

When an inmate enters the system, a health assessment is swiftly done to determine whether a prisoner needs a single cell, he said.

He insisted that if Pistorius were given a prison term, the hospital section of Kgosi Mampuru prison in Pretoria had the facilities to accommodate his needs.

"There should be no doubt in the minds of South Africans that Mr. Pistorius and any other inmate with disabilities will be accommodated properly," he said.

Overcrowding is an issue across the prison system, he acknowledged, but has been reduced from a rate of 63% in 2005 to 31% today.

Asked about the problems of gangs and violence in prisons, Modise said that more needs to be done to eradicate gangs outside the prison system and that within the system, authorities are dealing with the issue.

Roux, in questioning Modise, made the point that whether Pistorius was given a single cell in the hospital section of Kgosi Mampuru would depend on those evaluating his case when he entered prison.

However, Modise's testimony indicates that he does not think Pistorius should be held in the general section of the prison, Roux said.

He also raised concerns about what illnesses Pistorius could be exposed to in the hospital section -- tuberculosis is a problem in South African prisons -- and the levels of medical staffing.

Probation officer Annette Vergeer, who testified earlier in the week, said she did not think that South Africa's prison system could cater adequately to a vulnerable prisoner like Pistorius.

(CNN)