Even adult witnesses are often unreliable. There are all kind of issues with child witnesses. And those wold be verbal child witnesses. Child's memory also improves with age.
"Children testifying in court are perceived to be more honest than adults, but their limited memory, communication skills, and greater suggestibility may make them less reliable witnesses than adults."
Steps Can Be Taken to Improve Reliability of Child Witnesses
"Children testifying in court are perceived to be more honest than adults, but their limited memory, communication skills, and greater suggestibility may make them less reliable witnesses than adults."
Steps Can Be Taken to Improve Reliability of Child Witnesses