The main condition for the Qasamah process is the existence of "luth". Luth is a meaning of evidence and evidence that creates suspicion for the ruler that the murder is attributed to the accused, such as the presence of blood on his clothes or the possession of a bloody weapon. There are various questions about luth, such as its legitimacy, generality in the soul and limbs, the exclusiveness or allegoricality of the examples of luth... But the subject of this article is to determine the degree of belief that is achieved by the ruler through the Luth. Most jurists of both sects consider the realization of suspicion sufficient, but our claim, presented with a descriptive-analytical method in the context of contemporary jurisprudence, is that mere absolute suspicion is not sufficient to achieve Luth and execute the ruling by the Qasamah, and the ruler must definitely obtain ordinary knowledge (certainty). Our evidence is as follows:Prohibition of acting on suspicion except for what is spent on evidence, the violation of the rule of oath in terms of the use of oath by the claimant, the wisdom of mentioning Luth in narrations, the existence of opponents of the validity of Luth, caution in temperature, the rule of Dara, the possibility of acquiring ordinary knowledge for the ruler with new tools.