I concur in the judgment and in the opinion, except the reference to section 2061, of the Code of Civil Procedure. The instruction should be given only when made proper by some evidence. It is then to tell the jury that they must distrust a particular witness. This is an interference with the province of the jury which the legislature cannot authorize. It is prohibited by section 19, article VI, of the constitution.(See Kauffman v. Maier, 94 Cal. 269.)