The Bible, along with other sacred texts, provides solace and inspiration for billions across the planet. But how literally do its readers take passages such as this one?

If he smite him with an instrument of iron, so that he die, he is a murderer: the murderer shall surely be put to death.

Very literally, in some cases. Because this piece of scripture, from the book of Numbers (35:16) in the Old Testament, evidently provides some Christians with what they believe is "literal truth" and a biblical underpinning to their personal support for capital punishment.

When a man called Khristian Oliver stood trial for murder in Texas 10 years ago, several jurors consulted the Bible extensively during their deliberations. Key passages were highlighted and handed around among fellow believers. The "smite him" verse was one of them. One of these jurors later confirmed that reference to scripture played a part in his deliberation. In his view, biblical pronouncements always trumped man-made laws and he fervently believed that "the Bible is the truth from page one to the last page".

This juror, apparently just one of a four-fifths majority of jury members who introduced biblical notions into the jury discussion, also later made it very clear that he was a firm believer in capital punishment, describing life imprisonment as a "burden" on the taxpayer.

Did those religious, believing jury members cross an important line when they began looking up and discussing what they would have seen as "relevant" verses from an ancient text? Was it improper? Was it perhaps a well-intentioned, but deeply worrying deviation from the expected conduct of a jury?

A US appeals court certainly thought so. Last year, the court of appeals for the fifth circuit said that these God-fearing jurors "had crossed an important line" when they searched for guidance in scripture. It was, said this federal court, a more "egregious" example of this than had occurred in other jurisdictions. But federal appeals courts are extremely chary of overturning state courts' decisions. Oliver's appeal was dismissed. Surely the supreme court couldn't let this pass? In fact, because of growing disquiet in the US about a resort to Bibles in jury rooms, earlier this year a group of 46 federal and state prosecutors joined together in a petition to America's senior court urging it to examine the Oliver case to clarify law in this area. The supreme court declined to do so.

Oliver is now scheduled for execution on 5 November. He is left praying for either a rare clemency recommendation from the Texas board of pardons and paroles or, failing that, a stay of execution from the hardline state governor Rick Perry.

Human rights and faith often go hand in hand, a righteous belief in fairness and truth frequently linking arms with a fervent desire to ensure equality before the law and justice for all. Religion is a massively powerful fortifier to those suffering oppression and injustice. Prisoners the world over have held on to or even developed faith to see them through their mightiest challenges. Indeed, many of those within America's massive death row system survive the mental torture of years facing a gruesome death in a lethal injection chamber by turning to God.

But when biblical exegesis replaces the solemn, dispassionate weighing of evidence you know that things have gone badly wrong. It's one thing for a witness to swear on a Bible to tell the truth before a jury in a courtroom. It's quite another for those jury members to take the Bible back with them to the jury room to decide whether a man will live or die.