Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 151D, § 16

Trustees shall invest the funds of their pension plans and profit-sharing retirement plans and manage said affairs in accordance with the provisions contained in the instruments under which they are acting, or, in the absence of any such provisions shall invest the funds and manage fund affairs with the care under the circumstances then prevailing that a prudent man acting in a like capacity and familiar with such matters would use in the conduct of an enterprise of a like character and with like aims.