Is Under the Banner of Heaven based on a true story and where are Ron and Dan Lafferty now?

Is Under the Banner of Heaven based on a true story? You might have found yourself wondering as you watch the harrowing crime drama. 

Two years after it was first released, Under the Banner of Heaven has landed on ITVX and is available to stream for free in the UK for the first time. The miniseries tells a harrowing story of murder and faith and stars Academy Award winner Andrew Garfield as Detective Jeb Pyre and Gil Birmingham as Detective Bill Taba, with Daisy Edgar-Jones as Brenda Wright Lafferty. As they investigate the devastating murder of Brenda and her baby daughter in Utah, they uncover more about the origins of the Church of Jesus Christ of the Latter-day Saints.