Society needs to be protected from people such as the men convicted of the brutal attack on Hannah Cornelius and Cheslin Marsh, the State insisted in the Western Cape High Court on Thursday where it asked for at least three life sentences to be imposed on the students' assailants.

"The accused have no respect for human rights. They showed no mercy," advocate Lenro Badenhorst said during sentencing proceedings against Eben van Niekerk, Geraldo Parsons, Vernon Witbooi and Nashville Julius.

He submitted to Judge Rosheni Allie that Van Niekerk, Parsons and Witbooi be handed life sentences for the murder and rape of Cornelius, as well as for the attempted murder of Marsh due to the severity of the attack.

Badenhorst submitted that all four, except for Van Niekerk, should be sentenced to 15 years for the robbery. He said Van Niekerk should face 20 years as he was convicted for the same crime in 2013.

A "substantial period" behind bars would be fitting for the kidnapping as there was no prescribed minimum sentence for this charge.

The four are no strangers to serving time.

Multiple convictions

Witbooi had a 10-page rap sheet. He was first arrested in 1999 on a theft charge and had a range of convictions from burglary to robbery. He twice attempted to escape from prison and succeeded once.

He was released on parole in 2010 but violated the conditions and was rearrested to finish his sentence.

Parsons was previously convicted for burglary, theft and possession of stolen goods. He was released on parole in 2015.

Van Niekerk was convicted along with his brother of robbing a person of R2 500 at knifepoint only five years ago.

Julius has five previous convictions ranging from theft to drug possession.

The four were convicted of accosting Cornelius and Marsh in her VW Citi Golf at the corner of Jan Celliers Road and Bird Street in Stellenbosch in the early hours of May 27, 2017.

Victims robbed and forced into car

Cornelius was threatened with a screwdriver while Marsh was forced into the backseat of his friend's car at knifepoint.

Cornelius was pushed between the two seats and robbed of her purse and cellphone, while Marsh's clothes, cellphone, wallet, longboard, backpack and earrings were forcefully taken.

After the robbery, Julius left the scene.

Witbooi, Parsons and Van Niekerk then drove to the Helshoogte Pass, where Marsh was forced into the boot.

The accused took the now 22-year-old to a field near Bernadino Heights, Kraaifontein, where he was assaulted and stoned with bricks and left for dead.

Cornelius was then driven to a bush near a paintball range in Bottelary Road, where she was raped before being driven to Groenhof farm where she was stabbed to death.

Daughter's death 'beyond devastating'

Hannah's father, retired magistrate Willem Cornelius, took to the witness stand where he testified that he had been medically boarded well short of retirement age.

"Even without medical discharge, I would have resigned as I doubt that I could have retained the impartiality required of a judicial officer," he said.

He described the effect of his daughter's death on his family as "beyond devastating".

"My wife, in addition to being my best friend, was the strongest and most competent person I've ever met. She became a shadow of herself, inconsolable, frantic, almost manic in everything she did, outwardly still in control but with no substance underneath that façade," Cornelius testified.

"No one really knows what happened on that early morning when she decided to go swimming in an ice cold and stormy ocean. For myself I do not believe that she took her own life but I do believe that she did not have the physical or mental strength left to counter any difficulties that she may have experienced."

His autistic son does not understand the concept of death, he explained.

'What kind of people would do something like this?'

"Every night when I put him to bed, he stops in front of a framed photograph of Hannah and asks when her holiday is over and when she is coming home. Not a day goes by that he does not ask me at least a dozen times about his mother or demands her return as well.

"I am the last person in the world with which he has a meaningful relationship, and when I die he will be alone and institutionalised. We never expected Hannah to be financially responsible for his care, but we knew that his sister would be there to love him, and to be loved in return."

He asked Judge Allie for a sentence that will at the very least prevent other parents from going through what he and his loved ones have been through.

Marsh's mother, Marilyn was emotional when she recounted how her son had looked when she was called to the hospital after the attack.

"I asked myself 'What kind of people would do something like this? He didn't do anything to them," she said, weeping.

Parsons held his head in his hands before crying too.

Sentencing is expected on Monday.