The Supreme Judicial Court (SJC) for Suffolk County, also known as the single justice session of the SJC, is that part of the court's business in which an associate justice essentially acts as a trial judge, as was the function of the first justices, or as an administrator of the court's supervisory power under G.L. c. 211, § 3. The county court has original, concurrent, interlocutory and appellate jurisdiction conferred by the Massachusetts Constitution, statues, rules of court and case law. Practice before the single justice is governed by the Massachusetts Rules of Civil Procedure, S.J.C. Rule Two and pertinent Standing Orders.

Among the most common matters received are petitions filed pursuant to GL c. 25, § 5 (public utility appeal), GL c 112, § 64 (board of registration appeal), GL c. 156B, § 99 (dissolution of deadlocked corporation), GL c. 180, § 11A (dissolution of not-for-profit charitable corporation), GL c. 211, § 3 (superintendence), GL 214, § 1 (equity), 1 GL 231, § 1 (declaratory judgment), GL c. 233, § 20E (witness immunity), GL 249, § 4 (certiorari), GL 276, § 58 (bail review), GL c. 278, § 28E and Mass.R.Crim. P. 15(a)(2) (interlocutory appeal), and GL c 278, § 33E (gatekeeper).