Evidence gathered by police investigating the murder of Rory Blackhall would have been strong enough to charge the prime suspect.
Police have still to reveal details surrounding Rory's murder
The procurator fiscal studying the evidence also revealed that there was no evidence to implicate anyone else.
Simon Harris was found dead by officers investigating the 11-year-old's murder.
The police report said Harris, 37, asphyxiated Rory shortly after he abducted him on the way to school in Livingston last month.
Police told the procurator fiscal they believed Harris, who was on bail after being accused of abusing three girls, was acting alone.
A spokesman for the Crown Office and Procurator Fiscal Service detailed the fiscal's findings.
He said: "Following receipt of the police report into the circumstances of the death of Rory Blackhall, the procurator fiscal at Linlithgow can confirm at this stage that the available evidence would have been sufficient to charge Simon Harris with the murder of Rory Blackhall.
"The procurator fiscal has also confirmed that there is no evidence to implicate anyone else in this case.
"The Crown's investigation of the whole circumstances of Rory's death continues.
"While we can give no firm timescale for the conclusion of this investigation, which clearly requires to be thorough, it is also understood that it is in the interests of Rory's family and in the wider public interest that this be concluded as quickly as possible."
Rory, from the Adambrae area of the town, disappeared on Thursday, 18 August, after being dropped off near Meldrum Primary School.
Police had previously revealed that he had been asphyxiated but have not disclosed how this was done.