The police jail in question probably doesn't contain prisoners for more than 12 hours at a time and is more of a holding cell before they transport the prisoners to the local detention (county or city) center with more than 5 and under supervision for 24 hours... (I-3).
However, this doesn't alleviate the designer from designing the space being used for detention from meeting several requirements for an I occupancy...........
Structures or portions of structures shall be classified with respect to occupancy in one or more of the groups listed in this section. A room or space that is intended to be occupied at different times for different purposes shall comply with all of the requirements that are applicable to each of the purposes for which the room or space will be occupied. Structures with multiple occupancies or uses shall comply with Section 508. Where a structure is proposed for a purpose that is not specifically provided for in this code, such structure shall be classified in the group that the occupancy most nearly resembles, according to the fire safety and relative hazard involved.