What is the established ruling regarding mutual confession and denial in homicide cases?

Primary text

The established ruling, stated by Ahmad ibn Hanbal, is that if two witnesses testify against a defendant for murder, and upon his being brought for retribution (*Qawad*), a second person confesses to the act, the retribution (*Qawad*) is dropped against both the first and the second person. However, the second person (the confessor) is liable for the blood money (*Diyah*). The supporting evidence is a report where a man confessed to a murder committed by another, and Caliph 'Umar (may Allah be pleased with him) upheld the confession to save the wrongly accused from execution, stating that if the confessor had indeed killed someone, he had saved a life, thus dropping the retribution against the first party. The rationale is that the claim against the first defendant creates a doubt (*Shubah*) that warrants dropping retribution against the second, while the second person's confession necessitates the *Diyah* due to his admission of the act causing it. This view is considered the soundest and most just, supported by the prophetic tradition (Athar).