> The problem is we can't yet map a person's neurons well enough to know their motivations as to why they don't want to see the other person punished
We don't need to "map" Samantha Geimer's neurons to understand her motivations. We can listen to what she has to say herself about that topic, in her media interviews, in the book she wrote, on Twitter. Have you listened to what she has to say? Or are you saying that it doesn't matter what she says? Isn't that denying her a voice, and denying her agency? And, isn't denying her agency what Polanski did to her to begin with?
> This line of reasoning is part of why DV cases move forward even if the victim doesn't want to.
In many cases of domestic violence, the victim may still be under psychological domination by the abuser, and I agree in those circumstances there may be times when it is right to overrule the victim's wish that their abuser goes unprosecuted.
But in this case, Geimer and Polanski haven't see each other in person in over 40 years. She has had her own life – she married, had kids, a career. She explains her desire that the case be dropped as about what's good for her – escaping the continuing retraumatisation by the legal system and the media. I really don't see any evidence here that she is presently (or even recently) being psychologically dominated by Polanski.
If Geimer, as a thirteen year old, was arguing that Polanski shouldn't be prosecuted, I think it would be legitimate to overrule that wish. But, when she's arguing that as a fifty-seven year old, I don't think overruling her wishes is still legitimate. And, take note, her problem was not with the original prosecution in itself – she was happy with the original outcome that Polanski pled guilty and she didn't have to testify. Her objection is to the case being dragged on for decades against her will.
She's also angry about the judicial misconduct in the case – which, who cares about whether it hurt Polanski, it harmed her (the judge's unprofessionalism betrayed the victim); and by people who want to use the events of her life for political and media ends – it's her trauma not theirs, yet people want to use her trauma for their own ends without consulting her.
I get the impression a lot of people don't care about the actual detailed facts of this case, they just want to cling to the principle, and if Geimer's welfare and agency have to be sacrificed for their principle, so be it.