Beginning Tuesday on CNN's AC360, investigative correspondent Abbie Boudreau begins a four-part series looking into case of U.S. soldiers convicted of murder on the battlefield -- three Army sergeants who used their service pistols to execute four Iraqi men in their custody who they believed were insurgents.

Boudreau obtained nearly 24 hours of interrogation footage that includes a confession from one of the soldiers and raises several questions: on the battlefield, is murder a crime? And is the Army's policy on detainees realistic for soldiers on the battlefield?

Killings At The Canal: The Army Tapes begins Tuesday night on AC360, with an hour-long special airing Saturday at 8pmET.

> Update, Monday a.m.: In light of last week's events at Ft. Hood, CNN is holding this series until a later date.