Which of the following terms describes someone who is confined in a detention facility?

The term that accurately describes someone who is confined in a detention facility is "inmate." In a legal context, an inmate refers to an individual who is being held within a correctional facility, such as a jail or prison, as a result of a conviction or while awaiting trial.

The other terms have distinct meanings: a suspect is someone who is believed to have committed a crime but has not yet been charged; a defendant is an individual who is facing charges in a court of law; and a witness is a person who has knowledge or information about a case but is not necessarily involved in any criminal activity. Therefore, "inmate" specifically connotes the individual's status of being in confinement as part of the correctional system.