In every criminal prosecution for libel, the truth may be given in evidence to the court and if it appears that the matter charged as libelous is. true, and, moreover, that it was published with good motives and for justifiable ends, the defendant shall be acquitted.
Proof of the truth of an imputation of an act or omission not constituting a crime shall not be admitted, unless the imputation shall have been made against Government employees with respect to facts related to the discharge of their official duties.
In such cases if the defendant proves the truth of the imputation made by him, he shall be acquitted.