A mom who says her 7-year-old pulled the trigger. And a medical examiner who speaks for the dead.

In suburban Boston, years after the death of a pregnant 23-year-old was ruled a suicide, the FBI arrest a former local detective for her murder. In Lake County, Florida, a mom on trial for her husband's murder is raising a wildcard defense: her daughter did it. And Dr. Mary Jumbelic answers our question: how can medical examiners reach different conclusions in the same cases? NBC Boston's coverage of Sandra Birchmore's case Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.