If a person who has been duly summoned and required to attend as a witness under the preceding sections or section thirty-seven of chapter two hundred and eighteen fails, without a sufficient excuse, to attend, he shall be liable to the aggrieved party in tort for all damages caused by such failure.
Mass. Gen. Laws ch. 233, § 4
Liability for nonattendance
Official source: Massachusetts Legislature. Reproduced from public-domain Massachusetts statutes; confirm against the official source for the current text. Not legal advice.