I don't agree with emsr2d2 in post #4.
I don't wish to make this question unnecessarily complicated but I do feel that this can in some cases lead to confusion. There is nothing about the tense in itself that means that the person is still in prison now, even though that is extremely likely to be what is meant and what is interpreted. In terms of meaning, we can say that there is only an implication that he is still in prison. Without context, the use of the present perfect implies that he's still in prison rather than means it, which is not quite the same. There may be contexts where it doesn't mean that.