Mo. Const. art. I, § 8
That no law shall be passed impairing the freedom of speech, no matter by what means communicated: that every person shall be free to say, write or publish, or otherwise communicate whatever he will on any subject, being responsible for all abuses of that liberty; and that in all suits and prosecutions for libel or slander the truth thereof may be given in evidence; and in suits and prosecutions for libel the jury, under the direction of the court, shall determine the law and the facts.