2. In contracts, the parties are bound to toll the truth in their dealings, and a deviation from it will generally avoid the contract; Newl. on Contr. 352-3; 2 Burr. 1011; 3 Campb. 285; and even concealment, or suppressio veri, will be considered fraudulent in the contract of insurance. 1 Marsh. on Ins. 464; Peake's N. P. C. 115; 3 Campb. 154, 506.
4. When a defendant is sued civilly for slander or a libel, he may justify by giving the truth in evidence; but when a criminal prosecution is instituted by the commonwealth for a libel, he cannot generally justify by giving the truth in evidence.
5. The constitutions of several of the United States have made special provisions in favor of giving the truth in evidence in prosecutions for libels, under particular circumstances. In the constitutions of Pennsylvania, Delaware, Tennessee, Kentucky, Ohio, Indiana and Illinois, it is declared, that in publications for libels on men in respect to their public official conduct, the truth may be given in evidence, when the matter published was proper for public information. The constitution of New York declares, that in all prosecutions or indictments for libels, the truth may be given in evidence to the jury; and if it shall appear to the jury that the matter charged as libelous, is true, and was published with good motives and for justifiable ends, the party shall be acquitted. By constitutional provision in Mississippi and Missouri, and by legislative enactment in New Jersey, Arkansas, Tennessee, Act of 1805, c. 6: and Vermont, Rev. Stat. tit. 11, c. 25, s. 68; the right to give the truth in evidence has been more extended; it applies to all prosecutions or indictments for libels, without any qualifications annexed in restraint of the privilege. Cooke on Def. 61.