Society protects children from exposure to worldly matters. Society's norm anticipates sexual innocence. Children should be incapable of describing such things. It shocks the senses to hear a little girl speak about fellatio. Such age-inappropriate knowledge compels an inference of child sexual abuse.
Common sense shuns any other explanation.
When a child displays unique sexual knowledge and assigns it to experience with a defendant, the inference of guilt is overwhelming. As a rule, children are not sexually schooled or sexually active. The correctly held and widely accepted notion that children are sexually innocent fortifies inferences of guilt drawn from age-inappropriate sexual knowledge. The absence of sexual innocence, evinced by display of sexual knowledge, compels the conclusion that sexual abuse indeed occurred and that it occurred with the identified abuser. Additionally, child sexual abuse is commonly considered to be isolated in nature.