Ok, taking the question literally, a child should be responsible for any crime from birth. It's down to definitions such as 'crime'. However, I understand what you are asking.....such as when a child of say....11......'murders' a child of say...8? It's a tough one to answer even from somebody who works with kids of all ages all the time. Maybe it's one of those that has no dividing line, and each case has to be treated seperately, even though it opens itself up to arguments about subjective decisions. I'm glad I don't have to make the law.
The second part is a bit of a spin off from the first but maybe even more complicated. I don't believe in changing history. For instance, St. Petersburg/Leningrad. So, apersons past is their past....end of story. The problem is how that past is viewed. It should be the case that people are intelligent enough to understand that it is the past, and to understand what that means. However, I know most peole are not, and that we have to make do, so maybe that's a yes, they should, under the circumstances.
Rob.