Quoted from Amnesty Internation's site (maybe you should visit it Astral)
During her trial, Sakineh Mohammadi Ashtiani retracted a ‘confession’ that she had made during her pre-trial interrogation. Sakineh alleged that she had been forced to make the ‘confession’ under duress, and denied the charge of adultery. Two of the five judges found her not guilty, noting that she had already been flogged and adding that they did not find the necessary proof of adultery in the case against her. However, the three other judges - including the presiding judge - found her guilty on the basis of ‘the knowledge of the judge’, a provision in Iranian law that allows judges to make their own subjective, and possibly arbitrary, determination whether an accused person is guilty even in the absence of clear or conclusive evidence. Having been convicted by a majority of the five judges, Sakineh Mohammadi Ashtiani was sentenced to death by stoning.