A man has been jailed for life after admitting the rape and murder of his two-year-old niece in Leeds.
Mullen strangled the two-year-old with a ligature
Michael Mullen, 21, raped and then strangled Casey Leigh Mullen in her bed at her home in Gipton in February while her parents were downstairs.
A judge at Leeds Crown Court told Mullen he would serve a minimum of 35 years for the killing.
Describing Casey as "a special little girl", her family said she would always be in their hearts.
The court heard how an image of the little girl, naked from the waist down, had been found on Mullen's phone.
Police also found sexual images of children on his computer - one of which involved sadism - which had been downloaded between October 2006 and February this year.
Casey lived in Oak Tree Crescent with her mother Samantha Canham, 21, father David, 20, and her three-year-old brother.
On the night of 11 February, Mullen arrived at the home with David, his brother, after an afternoon of drinking.
The court heard Mullen had gone upstairs and was later found asleep next to Casey in her bedroom, though it was not unusual for family members to lie with the toddler as she slept.
As David and Ms Canham's brother Lee prepared a hot chocolate for the youngster, Mullen came downstairs, appearing "in a rush to get out of the house".
The Mullen brothers then went by taxi to their mother's house in Meanwood.
Minutes later Casey was discovered upstairs, covered in blood.
When Mullen was arrested at his home, he was "shaking uncontrollably" and later claimed to have had no memory of what had happened.
Neighbours said Casey Mullen was known as "Smiley"
Sentencing Mullen, Judge Mr Justice Simon said: "Those bare outlines are dreadful enough, but what is particularly horrifying about this crime is that she was your niece and she was a child of two years and two months.
"The rape and murder of this little girl by someone she trusted and loved were appalling crimes."
Quoting from a psychiatric report, he said: "You are a very dangerous man who is capable of lethal, violent, sexual crimes against children and you will continue to be so for the foreseeable future."
Following the hearing, her parents issued a statement.
They said: "We have some very happy memories of Casey Leigh and she will always be in our thoughts and in our hearts.
"She was a special little girl. We thank the good people of Leeds and particularly all those who sent us cards and letters. Those were a great comfort to us.
"We would now like to get on with our lives in peace and attempt to come to terms with the events of the last few months."
Senior investigating officer, Det Supt Steve Payne said: "Michael Mullen committed an act of wickedness beyond belief. What he did is beyond the comprehension of a normal society.
"Casey Leigh Mullen lived a short life which was brought to a very brutal end by a man she should have been able to trust.
"Incidents of this nature are every parent's nightmare and, whilst for most of us it is reassuring to remember that such crimes are very rare, a young family is left with the great pain of losing their daughter."