A Military jury (or "Members", in military parlance) serves a function similar to a civilian jury, but with several notable differences. Unlike civilian courts, "Members" of the panel are literally "judge-and-jury" in a Military tribunal, due to the role that they play in a General Court-Martial (which is akin to criminal felony trials for civilians) or Special Court-Martial (which is similar to criminal misdemeanor trials for civilians). The panel — in addition to arriving at a verdict — also has the responsibility of sentencing the accused (military parlance for "the defendant"), should the accused be found guilty of the charges which have been brought forward by the "Trial Counsel" (or prosecuting attorney), which will happen to be a JAG.
Mechanics
Jury composition
A trio of members may suffice for a Special Court-Martial proceeding, even though greater numbers are allowed. Unlike civilian juries, the Military jury may consist of more than a dozen members. For a General Court-Martial to proceed, there must be at least five members present.
Nowadays, a "jury of one's peers" are commonplace for civilian criminal trials to proceed. However, Court-martial Members are typically commissioned officers, unless the accused elects that the member pool include enlisted personnel.