To have jurisdiction means that an entity has legal authority over a prisoner. To have custody of a prisoner, a facility must physically hold that person. Prisoners under a State’s jurisdiction may be in the custody of a local jail, another State’s prison, or other correctional facility. Some states are unable to provide both jurisdiction and custody counts. 

It is important to use custody counts when adding different populations. For instance, it is possible that inmates could be double counted if adding a jurisdiction prison count to a custody jail count (a portion of inmates may be under state jurisdiction, but in jail custody). If one uses custody counts, there should be minimal overlap between the populations.