Six years ago, the murder of Matthew Shepard shocked the nation and became a rallying cry for those fed up with violence against gay Americans. “20/20” (9 p.m., ABC) revisits the Shepard case and reveals little-known facts that may challenge some of the myths about the case popularized by the play and HBO TV movie “The Laramie Project.”

Correspondent Elizabeth Vargas spoke to many who knew both Shepard and his killers. She also spoke to both convicted murderers, Aaron McKinney and Russell Henderson, in their prison cells. McKinney, who has no chance for parole or release, now states that the Shepard killing had absolutely nothing to do with anti-gay feelings and everything to do with drug-fueled rage. In a surprising twist, acquaintances of McKinney reveal that, far from being homophobic, McKinney was a practicing bisexual.

• A two-hour “Dateline” (8 p.m., NBC) special presents “Tom Brokaw: Eyewitness to History,” recapping the newsman’s contributions since being hired by NBC News back in 1966. “Eyewitness” features clips from interviews with Mikhail Gorbachev, President George H.W. Bush, Gen. Norman Schwarzkopf, journalists Bob Woodward and Carl Bernstein, and other newsmakers.
• For those viewers with the day off, the Hallmark Channel offers a lazy-day marathon of family-friendly movies, including “Annie” (8 a.m.), “Pollyanna” (1 p.m.) and both versions of “The Parent Trap.” Hayley Mills, Maureen O’Hara and Brian Keith star in the original 1961 “Trap” (4 p.m.), while Lindsay Lohan, Dennis Quaid and Natasha Richardson appear in the 1998 remake (7 p.m.).