At the hearing in either of the cases provided for in the preceding two sections, the county commission shall receive all legal evidence as may be offered, for the purpose of ascertaining whether the presumption of death is established; or it may refer the matter to a fiduciary commissioner to take such evidence, and report his findings thereon. No person shall be disqualified as a witness by reason of relationship to the supposed decedent or interests in his estate. All the evidence shall be reduced to writing and preserved in the files of the commission with the record of the case.