Children do not have to lie. Unfortunately they are easily manipulated and convinced things happened which actually did not. The memory becomes real to them and they will spend the rest of their lives convinced it actually happened, even passing polygraphs.
We simply have to rely on the integrity of the justice system and sell everything we own to afford the level of defense it takes to fight false accusations-with absolutely no hope of ever getting the money back if the charges are dropped or there is an aquittal.
The system sucks but it is the best in the world. But keep in mind this is the same system which does stop many sick freaks from hurting kids.