See, I think I would see that person not as just "my child," but as "my child who killed my grandchild." In my family, that frequently triggers the "you're dead to me" involuntary response.
I am not just yakking. When I found out several years ago that a close relative had committed a terrible crime many years ago, but had managed to get away with it, thus escaping punishment once the statute of limitations ran out, I cut that person off. They were dead to me. When they did die, I refused to attend the funeral because I was not going to pretend to grieve. I had already grieved that the person I had thought I had known had never really existed, and in all likelihood had been a sociopath.
If the SOL had not run and it had been in my power, I would have done all I could to see this relative in prison.