This shows that qasāma is a sanctioned procedure—an independent, foundational rule of the Sacred Law that, where it applies, qualifies the general evidences.

Conditions for qasāma
Among the most important is the presence of al-lūth (strong circumstantial suspicion). This is manifest enmity between the victim and the person accused of killing him—such as blood feuds between tribes—or any rancor that makes it highly probable the suspect committed the crime. In such cases the heirs may swear the oaths against the alleged killer whenever they are reasonably certain he is the murderer, even if they were not eyewitnesses.

Shaykh al-Islām Ibn Taymiyyah (d. 728 AH) maintained that al-lūth is not limited to enmity; it includes every circumstance that strongly corroborates the claim, such as a group dispersing from around a slain man or testimony from people whose evidence is not legally admissible in homicide cases, and similar indicators.

Aḥmad said, “I resort to qasāma when there is laṭkh, when there is an evident cause, when there is enmity, and when the defendant is someone who would ordinarily commit such an act.”

Commenting on this, Ibn Taymiyyah observed, “He mentioned four matters: laṭkh—that is, disparaging talk about the defendant like rejected testimony; a clear cause, such as people scattering from the scene of a killing; enmity; and the fact that the accused is among those known for killing. This is the correct view.”

Imām Ibn al-Qayyim (d. 751 AH) said, “This is one of the finest instances of adducing evidence, for it relies on outward indications that overwhelmingly suggest the claimant is truthful, so it is permissible for him to …”