A second SJC appointment for Gov. Patrick.

Justice John M. Greaney, the longest-serving member of the state Supreme Judicial Court and a pivotal vote in some of its most significant decisions, announced yesterday that he will retire by year's end, creating the potential for a new dynamic on the state's highest court.

Greaney will turn 70 in April of next year, and state law forces him to retire by that age, making his departure somewhat expected.

But the announcement yesterday that he will retire to take a job at Suffolk University created a ripple effect in the state's legal community, prompting reflections on his years on the bench, some of his most critical decisions, and the future of the court.

"He is a justice who will very much be missed," said Joan A. Lukey, a partner with the law firm Ropes & Gray of Boston, who has won and lost verdicts decided by Greaney.

"He's one of those people who is so even-keeled that he brings great balance to the bench when he's part of your panel. He is one of those justices in front of whom it's comfortable to argue."

Greaney was appointed an associate justice in 1989 by then-Governor Michael S. Dukakis. He had served as chief justice of the Massachusetts Appeals Court and was a state Superior Court and Housing Court judge.

In his years on the bench, he has helped decide some of the most significant legal cases in recent memory, including the landmark ruling in Goodridge v. Department of Public Health in 2003 that affirmed the rights of gays to marry. In that case, Greaney wrote what is known as a concurrent opinion, a powerful second argument supporting the majority opinion.

He has also authored opinions on complex corporate cases and on at least one case that affirmed the separation of powers and the court's authority.

Greaney is known as one of the court's better writers, one who can articulate a point in a legal decision as clearly as he can on the bench.

UPDATE: More from the Globe and Herald.

SECOND UPDATE: Patrick officially tosses the 1913 law that effectively restricted out-of-state gay couples from getting married in Massachusetts. Plus, Matthew Richer on the flaws of Gov. Patrick.

THIRD UPDATE: More from the Globe.

FOURTH UPDATE: From the New York Times, the Boston Globe and the Boston Herald.

FIFTH UPDATE: From the Herald.