When an offender's whereabouts are completely unknown after efforts to locate them, what are they classified as?

When an offender's whereabouts are completely unknown despite attempts to locate them, they are classified as an absconder. An absconder specifically refers to an individual who has intentionally escaped or evaded supervision, typically by leaving the jurisdiction or failing to report to their designated authorities. This classification indicates an active effort on the part of the offender to avoid law enforcement or correctional oversight.

Differentiating this from other terms, a fugitive might suggest a broader context where the person is actively evading law enforcement, but not necessarily indicating their whereabouts are completely unknown. Being in custody refers to a state where an individual is apprehended and held by law enforcement or correctional facilities, while "on the run" usually implies active evasion but does not address the unknown whereabouts aspect as clearly as absconder does. Thus, the term "absconder" is the most accurate designation for someone whose location cannot be determined after diligent effort has been made to find them.