[Restorer]

Why wasn't he charged with statutory rape?

Because the only (presumably) witness is dead?

[mountaineer]

They wouldn't need the girl to testify that the man had sex with her, it seems to me. The authorities know the girl's birthdate, they can prove paternity of the baby, and the approximate date the girl was impregnated. If she was "under age" when impregnated, voila, statutory rape.