Section 49. If a person summoned before the registrars to answer such complaint appears before them, they shall examine him on oath, and shall receive such other evidence which may be offered in regard to the matters set forth in the complaint and, if satisfied that he is properly registered as a qualified voter, they shall enter in the register a statement of their determination of the facts required for registration. If the registrars are satisfied that he is not a qualified voter, they shall strike his name from the register. If they are satisfied that, although he is a qualified voter in the city or town, he is illegally or incorrectly registered in a ward or voting precinct other than the ward or voting precinct in which he is required by section three to be registered, and have determined the ward or voting precinct in which he is so required to be registered, and his place of residence therein, they shall change his place of residence as given on the register accordingly. If a person duly summoned as aforesaid does not appear as directed in the summons and the complainant produces sufficient testimony to make out a prima facie case, the name of such person shall be struck from the register; but if such person appears before the registrars before the election or town meeting following and shows sufficient cause for his failure earlier to appear, the hearing shall be reopened and the matter decided on its merits, as determined from the evidence presented on both sides. The complainant and the person complained of may be represented by counsel, and all witnesses may be cross-examined.