Pick up the paper & you read instances of people being hospitalized for chest pain soon after being arrested. Unless the mere act of being arrested induces such pain(unproven so far), we can only conclude that in most cases, this is a convinient excuse to swap the hard unwelcoming walls of jail with the cosy hospital bed.
Chest pain having several causes, it is quite difficult to diagnose. No doctor would dare issue a clean bill of goods to a patient in fear of the latter really being ill. The doctor would rather keep the patient under observation for 15days/1month during which time the person can seek bail, influence witnesses & enjoy 5 start amenities in that period.
Till medical science advances, the small number of genuine chest pain cases during jail time, would ensure that even the fakers get attention.