The true story missed out in Under the Banner of Heaven

Under the Banner of Heaven has landed on ITVX, giving viewers without a Disney+ subscription the chance to watch the chilling true crime drama starring Andrew Garfield.

The series, directed by Dustin Lance Black, examines the investigation into the murder of Brenda Lafferty and her baby daughter in 1984 by her brothers-in-law Dan and Ron Lafferty. The Lafferty family were members of the Church of Jesus Christ of Latter-Day Saints, and the brutal murders rocked the religious community in Utah.

Read more: 'Under the Banner of Heaven' review: Andrew Garfield stars in a sorry tale of blind faith

While it is a dramatised version of real-life events, the FX TV series does not tell the whole story, and it is only through reading Jon Krakauer's book of the same name that one is able to see the full picture. Here is everything that you need to know, but be warned: this article contains some spoilers for the series.

The true story missed out in Under the Banner of Heaven

Under the Banner of Heaven follows the investigation by detectives Jeb Pyre (Garfield) and Bill Taba (Gil Birmingham) to find out who killed Brenda Lafferty (Daisy Edgar-Jones) and her 15-month-old daughter Erica, and arrest them. Though the detectives are fictional, the case is very real.

After uncovering a number of secrets of the Lafferty family, the detectives race to capture Dan (Wyatt Russell) and Ron Lafferty (Sam Worthington) and they do so in the show's finale, but that is where the drama ends — the real case was far from over.

Following their arrest in August 1984, Ron and Dan Lafferty protested their innocence and claimed to have nothing to do with the murders of Brenda Lafferty or her infant daughter. Days before their joint trial was set to take place Ron Lafferty attempted to take his own life and, per Krakauer, was left in a coma for two days. As a result, the brothers were not tried together.

In January 1985, Dan Lafferty was tried for his part in the murders of Brenda and Erica Lafferty. He chose to defend himself in court rather than use the lawyers appointed to him by the court, and ultimately he was found guilty of two counts of first-degree murder.

After telling the jury that he would give himself the death penalty if he were in their position, the jury were split 10-2 on the matter. This meant he was given a life sentence because a unanimous vote is required for capital punishment to be passed down as judgement. In his book, Krakauer argued Dan Lafferty managed to narrowly avoid the death penalty by flirting with a member of the jury during the trial.

Ron Lafferty was tried several months later, and there was evidence presented in court that he claimed to have had "a revelation" from God to kill his sister-in-law and her child, which he shared with his brother.

The criminal was also found guilty of the murders, but unlike his brother the jury voted unanimously for him to receive the death penalty. He chose to be killed by firing squad, but died in prison at the age of 78 from natural causes.

Dan Lafferty is still alive today and is serving a life sentence, and he even spoke with Krakauer for his book. The author claimed that the murderer continued to have no remorse for the killings of Brenda and Erica Lafferty, with him saying to Krakauer that it was a "revelation from God that these lives be taken".

Under the Banner of Heaven is available to watch in full on ITVX now, it is also available to stream on Disney+.

Watch the trailer for Under the Banner of Heaven: