Mass. Gen. Laws ch. 152 § 7B
In any claim for compensation by an employee, which is denied by an insurer or self-insurer, no statement in writing signed by the claimant, or statement taken on a recording instrument, concerning the facts out of which the claim arose, given by such claimant, or a person in his behalf, to such insurer or self-insurer, or to an agent or attorney of such insurer or self-insurer, shall be admissible in evidence or referred to at the hearing of any such claim, or in any proceeding connected therewith, unless a copy of such statement or verbatim written transcript of such recorded statement has been furnished to the claimant, or to a person acting in his behalf, or to his attorney, within ten days after a written request therefor.
Mass. Gen. Laws ch. 152, § 7B