Johannesburg - The emotional and teary mother of murdered toddler Cuburne van Wyk, 3, asked her child's convicted killer in court on Friday why he took the young boy's life.Lizelle van Wyk, testifying in Afrikaans through an interpreter during sentencing proceedings, asked Katlego "Chicken" Mpoku, 27, why he killed her child."Cuburne was a sick child and I was still breastfeeding him and that is why I have not yet gotten any closure," Van Wyk told the High Court in Johannesburg, sitting at the Palm Ridge Magistrate's Court."I just want to know and I want him to answer me, why did he do it? Because this thing is still in my mind... What I want the court to do [is] impose a life sentence."As Van Wyk spoke, Mpoku, wearing a red hoodie, stared ahead hunched over in the dock in silence.The public gallery was full with both Mpoku's and Cuburne's family. Several of Cuburne's family members wore white T-shirts bearing his image.Strong circumstantial evidenceLumka Qoqo, for Mpoku, told Van Wyk that while her client had been found guilty, he still maintained that he did not kill Cuburne in August last year.Van Wyk replied: "As he says he did not kill the child, then who did kill the child? I want to know who killed the child, because he is saying he doesn't know."Mpoku was convicted last month of killing Cuburne. Judge George Maluleke told the court at the time that there was very strong circumstantial evidence linking Mpoku to the child's death.This was despite a lack of DNA evidence linking Mpoku to the missing toddler, who was last seen on August 6 last year. His body was found on August 9.Police had returned to where Van Wyk's body was found five days after its discovery to gather additional exhibits. The crime scene at that stage was not cordoned off.Mpoku had told the court he left Cuburne in a street where other boys were playing near a soccer field in Reiger Park in Boksburg.BreakdownVan Wyk, whose testimony was punctuated by stoppages so she could gather herself after breaking down and crying several times, told the court on Friday that she had left Van Wyk with his aunt on August 6 when she went to work.Upon returning in the late afternoon, she was met by her sister's husband who was under the impression the toddler was at home."After asking me that question, I threw my bag on top of the bed, then I went out to look for the child," she said.Qoqo objected, saying that Van Wyk was being allowed by the state to have new hearsay evidence "sneaked in", even though the state had the opportunity to call Van Wyk during trial.Prosecutor Annemarie Smith replied: "The point is, she is trying to get the background of how she [Van Wyk] found out of the situation."Maluleke, while noting Qoqo's objection, allowed Van Wyk to proceed, stating: "It is important for her to let us know how the crime impacted on her."Van Wyk told the court that when she could not find Cuburne, she called the police. Both the community and police searched for him.Van Wyk, Mpoku’s parents knew each other wellWhen Cuburne's body was discovered, Van Wyk said she went to the scene, but was not allowed to see her child.It emerged that Van Wyk knew Mpoku's parents "very well" and Cuburne had gone to play with Mpoku's siblings on previous occasions. Van Wyk told the court she knew Mpoku only by sight."I was comfortable with the fact that my child would go and play, but I would never [have] thought he can do it [kill Cuburne]," Van Wyk said.Qoqo said: "This child played at their home with the siblings of the accused [Mpoku] and he would come back safely? I put it to you, didn't you find it strange that someone who had seen the children playing, and for some reason, he decides... to kill him?"He's [Cuburne] been there and he's [Cuburne] has never been harmed... All I'm saying ma'am, is he [Mpoku] said he didn't do it."After Van Wyk stepped off the stand, Maluleke postponed the hearing to July 31 to allow an expert to submit a report and testify.