A notorious prison gang leader has threatened to have Oscar Pistorius "taken out" if he is sent to prison and receives any special considerations, Pistorius' lawyer told a court today.

Lawyer Barry Roux brought up the alleged threat to Pistorius while challenging a prison official's claim that the legless sprinter could be kept safe in South Africa's prison system.

Pistorius, 27, was found guilty last month of culpable homicide, the rough equivalent of manslaughter, in the 2013 shooting of his lover Reeva Steenkamp. The court is now hearing testimony in the penalty phase that will determine how much prison time – if any – that Pistorius will serve.

Two defense witnesses, a corrections social worker and a probation officer, said Pistorius should not be sent to prison and suggested house arrest instead. They said that Pistorius, a champion paralympic sprinter who relies on prosthetic legs for his mobility, would be vulnerable in prison.

In pressing for a prison sentence, the prosecution called acting national commissioner of correctional services Zach Modise who rejected claims by a defense witness that Pistorius would face inhumane conditions and the possibility of being assaulted if he is sent to jail.

"There were threats against Mr. Pistorius. Don't they bring this to your attention?" Roux asked Modise.

Modise said he was not aware of threats and none of them had been brought to his attention.

Roux produced a March 5 edition of the Pretoria News that included an interview with Khalil Subjee, the alleged leader of the 26s prison gang.

Reading from the article, Roux told the court that Subjee called the paper from a prison call box, saying: "If he thinks he is going to come here and buy his way to get computers and cellphones and a lavish lifestyle, he must know that will never happen for as long as I am around." Subjee is quoted by the paper saying Pistorius would "be taken out" if that was the situation.

The acting prison boss said that should if Pistorius is sent to prison, he would be kept in the hospital section, where his disability can be catered for.

A key person for the prosecution's case today was Steenkamp's cousin Kim Martin who testified that Pistorius must “pay for what he’s done,” and his apology to the family of the girlfriend he shot dead in 2013 was not sincere.

Martin’s testimony came on the fourth day of the athlete’s sentencing hearing, which is expected to end this week.

"My lady, I really believe the accused, Mr. Pistorius, needs to pay for what he's done," Martin testified before Judge Thokozile Masipa.

Martin said her family is seeking justice, not revenge, for the Valentine’s Day 2013 death.

"We just feel to take somebody's life, to shoot somebody behind the door who is unarmed, who is harmless, needs sufficient punishment," she said.

Prosecutor Gerrie Nel has presented a muted case for Pistorius to serve time in prison. Nel, known as the "bull terrier" for his aggressive style, frequently made Pistorius cry during the trial.

The prosecution's potentially most dramatic witnesses, Steenkamp's parents, announced this week that would remain neutral and not take the stand. They also said they were dropping a civil suit against Pistorius. The announcement came after it was revealed in court that Pistorius has been giving the parents about $530 a month since he shot their daughter.

Outside of the courtroom, a lobby group for people living with disabilities slammed Pistorius' attempts to avoid jail time.

In an open letter to Pistorius, the CEO of the QuadPara Association of South Africa (QASA), Ari Seirlis, told Pistorius that he should stop trying to avoid prison and "Stand up and shows us the man that you said you were."

The group said it wanted to ensure that people with disabilities had access to mainstream society.

"If you want to make a difference for the disability sector, please go to jail and make sure that they provide the necessary reasonable and accessible accommodations for yourself," the letter stated.

Pistorius' spokesperson says they are not going to comment on the letter.

Closing arguments are expected on Friday.

The Associated Press contributed to this report.