Marcia Clark began her legal career as a criminal defense lawyer. She went on to work as a prosecutor in Los Angeles. Prior to the O.J. Simpson case, she worked for eleven years in the Special Trials Unit of the District Attorney's Office, where she handled a number of high-profile cases. The prosecution of stalker/murderer Robert Bardo in the Simpson case. Beyond a Doubt, her book about the Simpson case, was published in May 1997 and rapidly became the number one bestseller on the New York Times, Wall Street Journal, Washington Post, LA Times, and Publisher's Weekly bestseller lists.

Guilt by Association, Guilt by Degrees, and Deadly Ambition are three novels by Marcia that feature Los Angeles Special Trials prosecutor Rachel Knight. The books have been optioned by TNT for a drama series. Marcia is serving as an executive producer on the project.