A man jailed for life for the rape and murder of his two-year-old niece was charged with raping a 12-year-old girl four years ago, it has emerged.
Mullen poses a danger for the foreseeable future, the judge said
But the charges against Michael Mullen, of Gipton, Leeds, were dropped on the day he was due to stand trial.
The Crown Prosecution Service (CPS) said evidence came to light which cast doubt on his alleged victim's story.
On Monday, Mullen was sentenced to at least 35 years in jail for the killing of Casey Leigh Mullen in February.
Leeds Crown Court heard how the "violent and dangerous" paedophile pounced on the toddler while she slept and then strangled her.
Mullen, 21, of Lawrence Road, Gipton, was arrested after his niece was found smeared in blood at her home in nearby Oak Tree Crescent on 11 February.
Sentencing Mullen at Leeds Crown Court, Judge Mr Justice Simon said: "The rape and murder of this little girl by someone she trusted and loved were appalling crimes."
Quoting from a psychiatric report, he added: "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."
In 2003, the then 17-year-old Mullen was accused of raping 12-year-old girl on school playing fields in Meanwood, Leeds.
Casey Mullen was found in a pool of blood in her bed
Mullen admitted having sex with the girl, but claimed she had consented.
In a statement on Tuesday, the CPS (West Yorkshire) said: "In 2003, Michael Mullen had been charged with two offences of rape of a 12-year-old girl on the advice of the CPS.
"The CPS keeps cases under constant review, and immediately before the trial, new evidence came to light which seriously undermined the prosecution case against the defendant.
"The new evidence highlighted inconsistencies in the complainant's evidence such as to remove a realistic prospect of obtaining a conviction for the original offence.
"The CPS consulted with the police and prosecuting counsel and discussed the new evidence with the complainant, following which the decision was taken to offer no evidence, a decision fully endorsed by the trial judge."