Sarah McLaughlin branded Liam Whoriskey an “evil monster” and urged him to reveal what he did to in the hours leading up to his death.
It comes after Whoriskey (25) was found guilty last week of the manslaughter of the defenceless three-year-old, who was found dead in his bed in his family flat at Colmcille Court in the Bogside on Sunday, September 17, 2017 around 10 am.
The court heard Kayden was repeatedly assaulted and died after suffering bleeding and a swelling of his brain as a result of 15 non-accidental injuries.
In an interview with the Sunday World, Sarah, sister of Kayden’s mum, Erin, said: “The thing is no one knows what went on before Kayden died.
“What did he do to him? He won’t say.
“If I was speaking to him directly, I would ask him, tell me what you did.
“All we have is the evidence we heard in court – the manslaughter verdict has given us some closure.”
Kayden’s mum was too distressed to be interviewed, but speaking outside court after the verdicts were returned, she said she hopes her former fiance “rots in jail”.
Sarah added: “It was so hard in court for us.
“We were very angry and agitated and annoyed, heartbroken.
“We were sitting there because of what he did to Kayden.
“And that was the hardest part – having to sit there and listen to the child’s injuries.”
She added: “He deserves the death penalty but unfortunately he can’t get that.”
Judge Philip Babington excused the 11 jurors of six men and five women for life.
He said he would sentence Whoriskey following a plea hearing at Derry Crown Court on Friday, November 29.