Well there is the problem of getting the fathers DNA. He does not have to give a sample.
But it could be obtained in other ways say a fathers brother, or the fathers father, sister or the girl herself.
A male relative is best because the DNA of the Y chromosome is passed from the father only. But of course this is only available if the child is male.
We have moved past that, a judge can order you to give DNA, no different than a finger print in the eye of the law.
DNA could be gotten from the father by court order, whether he wanted to give it or not.Depending on the girl’s age, that’ll give you a Rape 3d, or at best, a Rape 2d.
That aside, the girl’s testimony would be needed if forcible compulsion, i.e Rape 1st was involved.