Well you have the right to remain silent. So there’s that.
Beyond that though I’m not really sure. I thought it was fairly clear in the US for a persons rights, but you guys are all over the place these days.

You’re betting someone’s life on it no matter what.
I’m not willing to give up on someone, especially a child, just because of what might happen.

but I don’t think kids like him go from “literally a psychopath” to “normal adult”

Not with that attitude they don’t. Do you really think a 6 year old is beyond help?
They need to be removed from the parents, given proper psychiatric help and support, and placed with a loving family that can help them manage whatever issues they have.
I have a feeling that won’t happen though and part of the reason for this is because people believe that small children cannot be helped.