Mass. Gen. Laws ch. 277B, § 6: Powers and duties of attorney general and assistant attorney general

Section 6. The attorney general or an assistant attorney general shall attend each session of a statewide grand jury and may prosecute any indictment returned by it. The attorney general or assistant attorney general shall have the same powers and duties in relation to a statewide grand jury that the attorney general or assistant attorney general has in relation to a county grand jury, except as otherwise provided by law.