[sam-s]

Same reason Gulag prisoners were released. It's a bureaucracy. The law says that this "crime" warrants a 15 year sentence. So he is sentenced to 15y. He is kept in the same labor camp with thieves &c. If he survives, he walks, because that's what the bureaucratic protocol says. Sometimes there is a separate rule that people like him are to be given an extra, say, 5 years for some "regime violation". However, the point is that if _all_ political crimes warrant a life sentence, then the deterrent value of prison disappears.