Longtime New London prosecutor Peter A. McShane, who has tried high-profile criminal cases and supervised the busy Broad Street courthouse, has been promoted to state's attorney for the Judicial District of Middlesex.

McShane, 49, of Madison, will succeed Timothy J. Liston, who retired Oct. 1 after 34 years of service. He said in a phone interview this afternoon that he would start his new job immediately.

"I'm excited," McShane said. "Middletown has wonderful prosecutors and a good relationship with the local bar."

On the other hand, he said, "It is sad to leave such a great bunch of people in New London." He said he "grew up" professionally here, and that New London will always be a special place for him.

State Supreme Court Justice Richard N. Palmer, chair of the Criminal Justice Commission, announced the appointment this afternoon after the commission interviewed candidates at the Division of Criminal Justice headquarters in Rocky Hill.

"We have every confidence that he will serve in the same great tradition as Mr. Liston," Palmer said. "We also wish to extend our congratulations to Mr. Liston on his retirement and our sincere gratitude for his many years of dedicated service."

McShane was appointed for a term expiring June 30, 2018, which is the remainder of the eight-year term to which Mr. Liston was appointed in 2010. The state's attorney is the chief law-enforcement officer for the Middlesex Judicial District, which includes the city of Middletown and the 14 other communities in Middlesex County.

The state's attorney is responsible for the supervision of the prosecutors' offices at the Part A Judicial District and Geographical Area No. 9 courts in Middletown and the Superior Court for Juvenile Matters in Middletown.

McShane joined the Division of Criminal Justice in September 1988 as a deputy assistant state's Attorney at G.A. No. 10, New London, where he has served as supervisory assistant state's attorney since February 2007. He has tried approximately 45 cases and has briefed and argued 26 cases before the Connecticut Appellate and Supreme courts.

He earned his B.A. Degree from St. Michael's College in 1984 and his J.D. from the Boston University School of Law in 1987. He received the 2011 Oliver Ellsworth Prosecutor of the Year Award from the Connecticut Criminal Justice Educational and Charitable Association.