Mass. Gen. Laws ch. 231 § 110
The appellate division of each district court shall have the powers of amendment of the trial court; shall have discretionary power to take further testimony and to render a decision based on such testimony; to decide issues of fact dependent upon issues of law or to direct a trial of such fact issues by a justice of the district court; to draw inferences from cases stated by agreement of the parties; and to render decision according to the justice of the case.
No new trial shall be granted in any civil action or proceeding in any district court on the ground of improper admission or rejection of evidence, or for any error as to any matter of pleading or procedure if the appellate division deems that the error complained of has not injuriously affected the substantial rights of the parties; and, if it appears to the appellate division that said error affects part only of the matter in controversy or some or only one of the parties, the court may direct final judgment as to part thereof, or some or one only of the parties, and may direct a new trial as to the other part only or as to the other parties.
Mass. Gen. Laws ch. 231, § 110