I doubt that any statistics are available, or any that could be taken as trustworthy. Is it not sufficient to note that it is prevalent enough to be common knowledge? And to note that if we really gave a damn what happens to these men, it would be easy enough to prevent?
Perhaps this is too much of a hijack, the original thesis seems to be that Mr. Pinter is comparing our criminal system with a political system of repression, which is, as shown, wide of the mark indeed. I will not pursue this further, my point is well taken, I think, but it is not directly germane to the issue.