Do the guards forget and hope those in the past forget after shft happens that they will not come back for payback for the petty cruelties or imagined slights?
you can clearly see there are gangs/ crazies now with police on the execution radar, you think if things went bad they would not come for their own and more recruits? Just like no one anywhere has a list with a prepper on their list as easy food supply.
and what of those in military prisons? How about the foreign troops inside your borders as UN, what will they do when they cant get home?