What is the ruling of the Sharia concerning a prisoner: Is he considered a traveler for whom it is permissible to shorten prayers as long as he is transferred between prisons, or is he like a resident who must offer full prayers?

A prisoner unjustly detained may shorten prayers, even if his captivity is prolonged, as long as he does not intend to reside (i.e., he has not resolved to stay and made an intention for it). However, one who is rightfully imprisoned may not shorten prayers. The unjustly detained is permitted to shorten prayers because he does not know when he will be released from his imprisonment. If the duration of his imprisonment is specified and it is more than four days, then he is not allowed to shorten prayers. But if he does not know whether he will be released today or tomorrow, then he may shorten prayers.