A Killer Story review – this tale of two relentless armchair detectives is prestige true crime

Eileen and Keen Umbehr were convinced the wrong person was convicted for double-homicide. After sending Pulitzer-winning journalist Joe Sexton 2,714 emails about it, he agreed to investigate – and it led to a messy entanglement HBO is no stranger to true crime, though its offerings tend to be more prestige than your average, with documentaries such as the unrelenting sex…