The Kyran Durnin case is indicative of real problems with Ireland's child protection systems, according to the State's special rapporteur on child protection, Caoilfhionn Gallagher.
Gardaí suspect that Kyran may have died in 2022 when he was aged six.
Officers continue to search a former family property and adjoining lands in Dundalk, Co Louth.
Now in its third day, investigators are carrying out a thorough search in and around the property.
A digger was seen working in wasteland directly behind the terraced house as part of the investigation into the suspected murder of the schoolboy.
Last week, gardaí opened a murder investigation months after Kyran was reported missing along with his mother.
The youngster’s mother has been located, but investigators say the whereabouts of Kyran remain unknown and he is now presumed dead.
Ms Gallagher, an Irish-born barrister at Doughty Street Chambers in London who specialises in human rights and civil liberties, said the case was deeply concerning.
"On the face of it, it looks as if our systems were not fit for purpose, they failed Kyron, and it's taken two years for us to catch up on what's happened,” she told RTÉ radio’s News at One.
"It is a horrifying case and there are many unanswered questions at this stage while the Garda investigation is ongoing.
"But from what we do know, a child apparently went missing from the face of the planet for two years and that was not picked up. And we're only now uncovering what may have happened in 2022, in 2024. So that's deeply concerning.
"I share the concerns that have been expressed by many Ministers and An Taoiseach and indeed by the Children's Rights Alliance about what's happened here. But it's also worth saying that this case is occurring against a backdrop of growing concerns in relation to child protection."
Ms Gallagher also said she agreed with a call from the Children’s Rights Alliance for a broader inquiry into the Kyran Durnin case.
“I welcome the fact that Tusla is conducting an internal review, but there has got to be a review outside the Garda investigation. Not just on the criminal issues, but on the broader systemic questions about what, if anything, went wrong here."
The key issue was how quickly lessons could be learned from any investigation, she added. "Because this isn't just about looking back. It's about looking forward to ensure that lessons are learned and that children are protected today and going forward. This can't wait."
