BBC Four

In NCIS: Origins, young Leroy Jethro Gibbs starts his career as a newly minted special agent at the fledgling NCIS Camp Pendleton office where he forges his place on a gritty, ragtag team led by NCIS legend Mike Franks.

Karl Alberg moves to a quiet coastal town to soothe a psyche that has been battered by big-city police work. But this gentle paradise has more than its share of secrets, and Karl will need to call upon all the skills that made him a world-class detective in solving the murders that, even in this seemingly idyllic setting, continue to wash up on his shore.

Sheriff Country focuses on straight-shooting sheriff Mickey Fox, the stepsister of Cal Fire's division chief Sharon Leone, who investigates criminal activity as she patrols the streets of small-town Edgewater while contending with her ex-con father, Wes, who is an off-the-grid marijuana grower, and a mysterious incident involving her wayward daughter.

The UnXplained will tackle subjects that have mystified mankind for centuries, from mysterious structures and cursed ancient cities to extraterrestrial sightings and bizarre rituals. The series will also feature contributions from top scientists, historians, engineers and researchers - each seeking to shed light on how the seemingly impossible can happen.

In the criminal justice system, the people are represented by two separate, yet equally important, groups: the police, who investigate crime; and the district attorneys, who prosecute the offenders. These are their stories.