The eight-episode show is described as a "gripping in- depth dramatisation" of the famed murder case that took America by storm in the early 1990s. When the Menendez brothers were tried on national TV for brutally killing their parents in Beverly Hills.
Nicholson will play Jill Lansing, who is genuinely dedicated to the Menendez brothers' defense.
The 45-year-old actress joined the previously announced cast Edie Falco as Leslie Abramson; Anthony Edwards as Judge Stanley Weisberg; Gus Halper, who will play older brother Eric; and Miles Gaston Villanueva, who will portray younger brother Lyle.