Trustee's claim acceptance in jurisprudence and civil procedural law

If a dispute arises between the owner and the trustee and in this case, trustee is the claimant and he does not have any reason to prove his claim, there are some controversy about acceptance or rejection of his claim. Civil Procedure Law has no specific provision in this respect. Shiite scholars in some cases like claim of waste and declaring lack of abuses and wastage accept trustee’s word. Even some of shitte scholars express a rule so-called “validation of trustee s word”. However, it seems that the popularity of absoluteness of this opinion or exemption of trustees word from bearing the burden of proof is due to prevalence of the cases which the dispute is about trustee’s duty of protection and skill to do something, and the owner claims trustee’s negligence about the duties. But in other cases that there are specific duties, like the time the trustee is a calimant or lawyer this rule is not useful and the trustee according to principle, should bring reason to prove his claim.