Prof Eileen Munro told ITV News the Serious Case Review into Daniel Pelka's death is "very frustrating".
Prof Munro, who conducted a review into high-profile abuse cases including the death of Baby P, said the new report "tells you what happened, but it gives you very little idea of why".
She continued: "These were clearly professionals who were concerned about Daniel, they were very actively trying to help him and they failed.
"And I don't get a sense from the review of why they failed - what it looked like, how they were misled, why they didn't see the sadistic torture that was going on - so I find I cannot clearly see what lessons you can draw from it."
Opportunities to protect Daniel Pelka, who was beaten to death by his mother and stepfather, 'were missed' a serious case has revealed.
Daniel Pelka's Serious Case Review is strong on what went wrong, but weak on explaining why it was allowed to happen.