The prosecution described her injuries as similar to those one would suffer in a high speed car crash.
The court heard that the Gray helped Butler cover up the fact that he had lost his temper and beaten the little girl to death.
The pair reportedly re-arranged the six-year-old’s room to make it appear as though she had fallen off her bed, and sent her younger sibling into the room to “discover” the body, reports The Telegraph, before finally calling emergency services two hours later.
"Thus it is that when, on October 28, you feeling under the weather and trying to catch up with your chores, lost your temper with Ellie and attacked her with lethal violence, it was not a tragic aberration but was all too consistent with your treatment of, and your attitude towards, her,” said the judge.
The court heard that Butler was “angry, overbearing and manipulative" with a "volatile temper" which could "explode at any time", reports mamamia.
Butler reportedly sent hundreds of texts threatening Gray along with their two children in the months leading up to the incident.
The court also heard how he physically abused both Gray and Ellie on several occasions, with the child reportedly suffering a broken shoulder.
A witness statement provided by Butler's ex-girlfriend, Hannah Hillman, also added to the prosecutions case, describing him "pure evil". This statement was not given to the jury reports The Telegraph.
The Judge described Gray as "exceptionally naive and stupid" for helping Butler cover up the crime, reports the BBC.
He added: "You played your full part in the grotesque charade that was the 999 call whilst subjecting your dead daughter to the indignity of pointless CPR when you knew full well she had been dead for two hours."
Gray’s mother, Linda, who had cared for Ellie with her husband Neal when their parents lost custody, died on the first day of the murder trial.
In a joint statement written ahead of the trial, the grandparents said: "Our lives have changed so dramatically due to the impact and shock and horror of this event that we struggle every day to deal with the reality of the death of our dear granddaughter Ellie. She was our shining light."
"We did not realise that some people could be so wicked in life,” they added.
During sentencing, Judge Justice Wilkie told Butler he was a “self-absorbed, ill-tempered, violent and domineering man”.
“[You] regarded your children and your partner as trophies, having no role other than to fit in with your infantile and sentimentalised fantasy of family life with you as the patriarch whose every whim was to be responded to."
Butler has been sentenced to 23 years in jail for the murder of Ellie, which he has said he will appeal.
"I'll fight for the rest of my life - unbelievable," before adding: "I want to be sentenced now so I can fight in the Appeal Court."
"I will fight forever to prove this wrong. My daughter was jumping in the house. I'm 100% not guilty."