defamation, libel and slander.— When a person is prosecuted or sued for making or publishing an imputation of a defamatory, libellous or slanderous nature, the Court shall not, before it has recorded its findings on the issues whether such person did make or publish such imputation, and whether such imputation is true, permit any question to be put to any witness for the purpose of injuring the character of the person in respect of whom such imputation has, or is alleged to have, been made, or any other person, whether dead or alive, in whom he is interested, except in so far as any such question may be necessary for the purpose of determining the truth of the imputations alleged to have been made or published.