Daynes had bought condoms and a tape to tie up his victim a month before the killing.
"Following the infliction of the fatal injury to Breck Bednar, Lewis Daynes disseminated images of his body to at least two people as well as making contact with a member of his online community to tell them that he was dead," said Richard Whitham QC, outlining the prosecution's case.
He said there was evidence of sexual activity between the two before the killing.
Breck's triplet siblings, then aged 12, learnt of his death when they were texted photos of the body by others.
Daynes then called police and told them Breck came at him with a knife during an altercation.
He also submerged his computer in water to destroy evidence.
It could be reported yesterday that Daynes had been accused of rape in 2011 against another boy when they were both 15.
The investigation ended with a decision by Essex police not to go ahead with the case.
The allegations were re-investigated after the murder and Daynes was charged with five offences including rape, attempted rape and possessing indecent images.
Daynes had denied the charges and they were subsequently dropped after the alleged victim declined to give evidence.
Essex police, which investigated the rape investigation, and the force in Surrey, which received the call from Ms LaFave outlining her concerns of Daynes' behaviour, are under investigation by the police watchdog.
"I believed that the police would help me," said Ms LaFave following the jailing of Daynes.
"I had given them enough information to check their systems to see that in fact Daynes was known to the police. We all make mistakes but incompetence in child protection is unacceptable."
She called on the British government to properly fund police investigations for offences involving children, and to share information between agencies.
Daynes, a computer engineer, had previously pleaded guilty to the murder of Breck at his home in Grays, Essex, in February last year.
Daynes had groomed Breck through the online community dedicated to war games and had sought to separate him from his family through a series of emails, Chelmsford Crown Court was told.
Daynes had behaved in a similar way to other boys including sending one a video of a man being beheaded.
Justice Cox told Daynes that his contact with Breck increased in a sinister way.
"The precise details of what happened in your flat are unclear and may never be known," she said. "I'm sure that this murder was driven by sadistic or sexual motivation."
The police watchdog said yesterday that the member of staff who took the call from Ms LaFave resigned from the force in August 2014.
Another member of staff faces a misconduct probe.
The watchdog said yesterday it was trying to find out if Surrey police properly trained its staff on child protection and was also investigating the response by Essex police to the rape allegation.
- Independent
