The possibility of miscarriage of justice
And has the news of the litigants reached you? When they climbed over the wall into [Prophet David’s] Mihrâb [a praying place or a private room]. When they entered in upon Dâwûd [David (as)], he was terrified of them. They said: “Fear not! [We are] two litigants, one of whom has wronged the other, therefore judge between us with truth, and treat us not with injustice, and guide us to the Right way. Verily, this my brother [in religion] has ninety-nine ewes, while I have [only] one ewe, and he says: “Hand it over to me, and he overpowered me in speech.” [Dâwûd (David [as])] said [immediately without listening to the opponent]: “He has wronged you in demanding your ewe In addition to his ewes. And, verily, many partners oppress one another, except those who believe and do righteous good deeds, and they are few.” And Dâwûd [David (as)] guessed that We have tried him and he sought forgiveness of his Lord, and he fell down prostrate and turned [to Allâh (swt)] in repentance. So We forgave him that, and verily, for him is a near access to Us, and a good place of [final] return [Paradise]. O Dâwûd [David (as)]! Verily! We have placed you as a successor on earth, so judge you between men in truth [and justice] and follow not your desire for it will mislead you from the Path of Allâh [swt]. Verily! Those who wander astray from the Path of Allâh [swt] [shall] have a severe torment, because they forgot the Day of Reckoning.[13]
Even Prophet David [as] was susceptible to make poor judgements.
Therefore in the case of murder, there will always be the possibility of a miscarriage of justice.