what evidence is needed if a statutory rape case goes to court? do all they need is the girls word?

Answer 1

The girls word is probably not enough. Keep in mind, all that must be proven is that the act occurred. Consent is NOT a defense, Belief that the 'victim' was of legal age is NOT a defense. Seduction by the 'victim' is NOT a defense.

Answer 2

Usually it takes a bit more than just the victim's word. Something like witnesses that saw the girl with the accused. DNA or physical evidence of any kind will also help the case.

If nothing else, physically distinguishing marks of the accused might be entered into evidence to compare with the descriptions the victim recounts. That is what they did with Bill Clinton.