Laura Coates delves into new theories about the 1975 murder of Martha Moxley, how Robert F. Kennedy Jr. investigated a potential eyewitness, and how Martha's mother copes without justice.

A new look at Michael Skakel's 2002 trial to learn how prosecutors put him in jail, how defense lawyers got him out in 2013, and how a potential clue hints that two people might have killed Martha Moxley.

Laura Coates re-explores the tragic 1975 murder of 15-year-old Martha Moxley to learn about a mother's quest for justice, what the crime scene and autopsy reveal about the killer, and how a break in the 23-year cold case ends in arrest. (Source: NBC)