HBO's new true crime docuseries "A Killer Story" examines the 2002 murders of Mike Sisco and Karen Harkness in Topeka, Kansas, and the campaign by amateur investigators Keen and Eileen Umbehr to overturn the murder conviction of Sisco's ex-wife, Dana Chandler. The three-part series, made by film-makers Matthew Galkin and Josh Levine with veteran journalist Joe Sexton, questions the safety of Chandler's conviction and highlights how ordinary citizens can shape the outcome of a high-profile murder case.

Chandler was initially not charged after the 2002 killings due to a lack of evidence placing her at the scene, but was arrested in 2011 following a change of prosecutor and a CBS "48 Hours" report, and was later sentenced to consecutive life terms. Eileen Umbehr, sceptical of the verdict, bombarded journalist Sexton with thousands of emails, while her husband Keen, a former garbage collector turned lawyer who won a US Supreme Court case in 1996, helped build the legal case that led the Kansas Supreme Court to review and ultimately overturn Chandler's conviction.