What to Watch Friday: New Janet Jackson documentary + true crime on Dateline, 20/20

Janet Jackson (8 p.m., LIfetime / A&E) - This new four-hour documentary marks the 40th anniversary of Janet Jackson’s first album, “Janet Jackson” in 1982. The filmmakers had full, unprecedented access to the singer, resulting in an intimate, honest and unfiltered look at her untold story. Producers filmed the documentary for over three years and had exclusive access to archival footage and never-before-seen home videos, along with star-studded interviews. In addition to her career, the film will look at Jackson’s private life for the very first time, and reveals some of her most intimate moments caught on camera. This new documentary airs across two networks on two nights, with the second part airing on Friday. In tonight’s first part, Janet’s father, Joe Jackson, puts her to work in the family show at the age of 7. Her father never asked if she wanted to be a performer, so it’s up to Janet to find her own path.

Dateline (9 p.m., NBC) - Josh Mankiewicz reports on the 1974 murder of a Ft Worth high school student who was kidnapped and murdered following a Valentine’s Day dance. Mankiewicz updates viewers on the cutting-edge DNA technology and police work that led detectives to identify Carla Walker’s killer more than four decades later. The report includes interviews with Walker’s former boyfriend Rodney McCoy, her family members, Ft. Worth detectives and more.

20/20 (9 p.m., ABC) - 20/20 tackles this nearly 30-year-old cold case: the disappearance of 27-year-old Mason City, Iowa, anchorwoman, Jodi Huisentruit. Huisentruit vanished early one morning and her whereabouts have never been determined. 20/20 co-anchor Amy Robach explores surprising new leads in the case, in a collaboration with investigative journalist Maria Awes.

Some programming descriptions are provided by networks.