The use of "reasonable doubt" as a standard requirement in the Western justice system originated in medieval England. In English common law prior to the "reasonable doubt" standard, passing judgment in criminal trials had severe religious repercussions for jurors. According to Christian law prior to the 1780s: "the Juryman who finds any other person guilty, is liable to the Vengeance of God upon his Family and Trade, Body and Soul, in this world and that to come."
It was also believed "In every case of doubt, where one’s salvation is in peril, one must always take the safer way.... A judge who is in doubt must refuse to judge."
It was in reaction to these "religious fears" that "reasonable doubt" was introduced in the late 17th century to English common law, thereby allowing jurors to more easily convict. Therefore the original use of the "reasonable doubt" standard was opposite to its modern use of limiting a juror's ability to convict.