Forensic anthropologist Dr Julie Roberts is giving evidence at the trial of Mark Bridger, accused of the murder of April Jones.
She was asked to examine fragments found in the fireplace at Mr Bridger's cottage in Ceinws.
She tells the court all of the fragments are burned human bone, in her opinion.
Dr Roberts says there is "very strong" evidence that three of five fragments are human skull, and "strong" evidence one fragment is human skull. The final fragment was not able to be confirmed.
She tells Mold Crown Court that one fragment is very characteristic of a human child's skull - in her view it comes from a child aged between four and eight.
A DNA test was performed on one fragment, but it was too badly burned, so no DNA could be obtained.
Mark Bridger denies murder, abduction and intending to pervert the course of justice.