Oscar Pistorius must "pay for what he's done" and his apology to the family of the girlfriend he killed was not sincere, a cousin of Reeva Steenkamp testified Thursday.

Kim Martin spoke on the fourth day of the sentencing portion of the double-amputee Olympian's trial. Following the testimony, which is expected to end this week, Judge Thokozile Masipa will rule on what punishment Pistorius must serve after convicting him of culpable homicide for shooting Steenkamp through a toilet door in his home.

"My lady, I really believe the accused, Mr. Pistorius, needs to pay for what he's done," Martin testified before the red-robed judge.

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

Just after the court adjourned for lunch, Pistorius' sister Aimee became tearful and distraught, telling her family that a man who was behind her in the gallery had mouthed an obscenity at her. Pistorius' brother, Carl, said he would inform police about the courtroom incident.

Marc Strydom and Mikey Schultz, two men who said they were in court to support Steenkamp's family, denied any involvement in the alleged incident.

"They're making up a fabricated story, same as Oscar's," Schultz said. "They're all a bunch of liars."

Schultz is a former boxer and the self-confessed killer of a businessman who escaped prosecution in an immunity deal with the state. He has been seen sitting in court this week with two men who have had altercations with Pistorius in the past.

Pistorius was acquitted of murder for the Feb. 14, 2013 killing and found guilty of the lesser crime of negligent killing. Masipa has wide latitude when deciding on a sentence for culpable homicide, and could order a suspended sentence and a fine, house arrest, or send him to prison for up to 15 years.

Testimony in the sentencing hearing ended Thursday. The prosecution and defense said they would deliver final arguments on Friday, clearing the way for the judge to deliver the sentence at a date yet to be announced.

Defense lawyers have argued for a sentence of three years of house arrest with community service. In the first part of the sentencing hearing, they called a psychologist and social workers, who said that Pistorius should not go to prison because of his ongoing emotional suffering. They also said his disability as a double amputee who needs prosthetic legs would leave him vulnerable in jail.

Chief prosecutor Gerrie Nel has called suggestions of a house arrest sentence as "shockingly inappropriate" and wants Pistorius to be sent to prison.

Martin, the cousin, said a prison sentence would be appropriate for Pistorius and that she understood the rehabilitation program in jail to be humane and dignified, contrary to allegations by one of the social workers who testified for the defense. In her sometimes emotional testimony, Martin said many people had suffered because of Pistorius, including his own family, and that a sentence that excludes jail time would encourage the athlete to "feel within himself that what he's done is all right."

Zach Modise, the acting national commissioner for correctional services, testified after Martin, saying that the South African prison system compared favorably with prisons he had visited in Britain and the United States. He acknowledged problems such as overcrowding and gang activity, but said officials had made progress in combatting those problems and that some prison facilities can cater to disabled criminals, including Pistorius.

"We will be able to accomodate him," Modise said.

However, defense lawyer Barry Roux referred to reports of an increase in alleged torture in South Africa's prison system. He also said an imprisoned gang leader alleged that Pistorius would be under threat if he is incarcerated; Modise said he was not aware of any threat.

At the beginning of Thursday's proceedings, Nel congratulated Judge Masipa on her birthday and people in the courtroom applauded.