This two-hour examination of the alleged assassin of President John F. Kennedy isn’t new. In fact, it’s 20 years old, from a Frontline special shown originally in 1993, marking what was then the 30th anniversary of the JFK assassination. But Oswald rarely is studied in this much detail – that was true then, and on TV, it’s true now, so this Frontline remains, after all these years, TV worth watching. Check local listings.