Leila Borrington, 23, killed Harvey Borrington, who had severe non-verbal autism, by slapping him "multiple times" in what the judge said was a "sustained violent assault".

The court heard Borrington had also attacked Harvey twice in the four months before his death which left him with a broken arm and marks on his face.

Nottingham Crown Court heard that Borrington lied about what had happened to Harvey when paramedics were called to her home in Jacksdale, near Kirkby-in-Ashfield in Nottinghamshire in August 2021.

She had claimed Harvey "fell backwards" off a one-seater leather sofa at home.

But the court heard she had inflicted "unsurvivable" injuries, including a skull fracture, on Harvey and sent a text message to his father that said: "Why does this happen to me?"

Harvey, who spent most weekends with Borrington, died in hospital on August 9, two days after paramedics were called and found him "deeply unconscious", "unresponsive" and with "abnormal body posture".

Passing sentence on Thursday, Mr Justice Nicklin told Borrington: "You were 21 when the first offence was committed and 22 when you assaulted and killed Harvey."

He told Borrington: "During the trial we saw video footage of Harvey playing with his toys and placing items into the dishwasher.

"Within less than 30 minutes, further video footage showed Harvey unconscious on the living room floor.

"Precisely what happened to Harvey only you know."

Prior to sentencing, Harvey's mother, Katie Holroyd, read a victim statement to the court, in which she paid tribute to her son as "the most loving little boy anyone could have wished for".

"Harvey's life was cruelly ended when he was only three years old," she told the court.

"To this day I cannot bear to think of him lying on the floor dying with her filming him and delaying getting medical help."

Describing Harvey's death as a recurring nightmare from which she will never be able to wake, Ms Holroyd added: "We will always treasure the short time we had to spend with him.

"She [Borrington] knew what she had done to him and she could have said so from the start."

Instead, Borrington had "chosen to lie, no doubt to try and save herself", Ms Holroyd said.

Prosecutor Jonas Hankin KC claimed that Borrington targeted Harvey, who communicated through hand gestures and a handful of words, because he was unable to articulate when he was in pain.

The judge also took into account the "history" of the use of violence by Borrington and her immediate response after Harvey was assaulted.

Text messages sent by Borrington after she had broken Harvey's arm in April 2021 showed "a shocking lack of care and concern" for the child, the judge also noted.

The stepmother was cleared of murder but found guilty of unlawful killing, wounding and assault last month.