Hint 20: The three culprits are family

[prof]

Pretty much. All of the kids have been proven innocent, with one exception.
And the only corpse inspections that a child culprit could lie about were the insepctions of that child's own parents. So, the culprit group was a family of two adults and one child.
Murder with the family. How sweet.
So, who are the three culprits? There's hardly any point in stretching this out further, is there?