AbstractIn the Civil Procedure Act, procedural defence set forth by the DEFENDANT regarding the deed relied upon by the claimant is raised in the form of denial, doubt or claim of forgery and it is silent in relation to other possible objections raised by the DEFENDANT, including rejection of a deed relied upon, SILENCE and the use of the phrase "I don't know" concerning the person to whom the deed is attributed. Canadian arbitrators have ordered online hearings over the opposing party’s objection. While in Imami jurisprudence, SILENCE and rejection, as well as "I don’t know", are mentioned as responses of the DEFENDANT to the claim of the plaintiff, along with the other responses of the DEFENDANT, i. e. confession and denial. This research aims to find the answer to the question that the DEFENDANT's use of the phrase "I don’t know" against a deed that is relied upon is compatible with which of his possible answers, i. e. denial, doubt, SILENCE or rejection of authenticity of a deed. The findings of this research, which were obtained with a descriptive analytical method and a comparative approach in Iranian law and Imami jurisprudence, indicate that the imami jurists, firstly, did not address the DEFENDANT's response in relation to the document in question,rather, they examined it concerning the claim brought against the DEFENDANT. Secondly, they did not mention any response from the DEFENDANT under the title of doubt, and they categorized the DEFENDANT's responses as confession, SILENCE, denial, and also what is considered to fall under denial. Meanwhile, the legislator has included the DEFENDANT's response in formal defense to consist of expressions of denial, doubt, or allegations of forgery, along with SILENCE. In cases of denial, doubt, or allegations of forgery, the court orders an examination of the authenticity of the document. In case of SILENCE, however, the default assumption is the validity of the submitted documents, and there is typically no evidence or reason to investigate the authenticity of the document. Almost all jurists have not included expressions of doubt among the responses of the DEFENDANT, considering the expression of denial sufficient to reject the claimant's request and viewing the response "I don't know" as a type of denial. On the other hand, Formal and substantive defenses regarding the submitted document do not align with the rule of "I don't know, " and one cannot, solely based on a declaration of unawareness and lack of knowledge regarding the existence or content of the submitted document, derive any effect from it. However, if the court encounters such a situation and the DEFENDANT is present, it should clarify the perceived formal objections and guide the DEFENDANT to express their intentions clearly.