Justice Martha B. Sosman of the Massachusetts Supreme Judicial Court, whose 2000 appointment gave the state's highest court its first female majority, died Saturday of respiratory failure, court officials said.
The 56-year-old jurist had been diagnosed with breast cancer in 2005.
Justice Sosman, a former board member of the Planned Parenthood League of Massachusetts and a founding partner of an all-female law firm in Boston, surprised some in the legal community by joining two other justices in dissent against the landmark 2003 decision legalizing same-sex marriage. She wrote that the majority opinion "merely repeats the impassioned rhetoric" of same-sex marriage advocates.
"A quick review of the résumé makes people leap to various conclusions about me," she told the Globe three years ago. "The five-woman firm, the involvement with Planned Parenthood, I think added to this image that I was going to be this crusading feminist liberal whatnot, which is certainly not what I am."
In a telephone interview, Margaret H. Marshall, chief justice of the Supreme Judicial Court, described Justice Sosman as "a jurist's jurist."
"In addition to her formidable intellectual talents, she had an almost unparalleled capacity to identify the critical legal issue in any case and to resolve the legal issue in clear, coherent prose, so that both the judgment of the court and reasoning of the court was readily understandable," Marshall said. "She could issue sentences from the bench that would make E. B. White proud that the English language was being used in such a way."
She was also a gifted pianist -- she often invited colleagues to her recitals -- a proud gardener, and a serious Red Sox fan, Marshall said. "She was extraordinarily hard-working, but she left plenty of time in her life to enjoy things," Marshall said. "She had a delicious sense of humor."
Justice Sosman is the first SJC justice to die while still serving since Justice Robert Braucher died at age 65 in 1981. Former Chief Justice Edward F. Hennessey, who retired in 1989 after reaching age 70, the mandatory retirement age for state judges, died last week at 88.
Governor Deval Patrick will nominate a replacement, whose appointment must be confirmed by the eight elected members of the state Executive Council.
In a statement, Patrick said, "I join the Court, the Bar and the general public in celebrating the life and service of Justice Martha Sosman. She was a wise judge and a good personal friend. She leaves a great void on the Court. My condolences go out to Justice Sosman's family and colleagues."
Born in Boston in 1950 and raised in Concord, Justice Sosman graduated from Carlisle Regional High School in 1968. She went on to graduate cum laude from Middlebury College in Vermont in 1972 and magna cum laude from the University of Michigan Law School in 1979.
Her first job as an attorney was with Foley, Hoag & Eliot in Boston, where she worked from 1979 to 1984. She spent the following two years as an assistant US attorney, until becoming chief of the Civil Division of the US Attorney's Office in Boston, a post she held from 1986 to 1989. She left the government that year to help found Kern, Sosman, Hagerty, Roach & Carpenter, P.C.
Justice Robert J. Cordy, who worked with her in the US Attorney's Office, helped recruit her as an associate justice of the Superior Court in 1993.
"As an attorney, from the moment anyone met her, they knew she was something special, as a person and as an intellect," Cordy said. "She was incisive in her understanding and her analysis of legal problems."
Cordy was appointed to the SJC shortly after Governor Paul Cellucci nominated her to the court on Sept. 6, 2000. "She's unlike anyone I ever met before," Cordy said. "She had a powerful intellect, stripped of any self-interest, ambition, personal agenda. It was a pure, raw, magnificent intellect . . . Her best thinking was never written, because it persuaded colleagues. She kept all of us honest. I can't imagine being on the court for another 12 years without her."
Justice Sosman, then 49, survived opposition to her nomination from abortion rights opponents.
Colleagues described her as fearless on the bench. When House Speaker Thomas M. Finneran, who exercised authority over the judiciary's budget, failed to fund the Clean Elections Law, she ordered the state to sell property.
"She was a first-rate talent by all accounts," said Jack Cinquegrana, president of the Boston Bar Association. "She was one of the most well-respected lawyers in the state."
But even those who admired her took issue with her decision to dissent against legalizing same-sex marriage.
"I always respected the integrity she brought to the bench and her awesome intellectual power," said Ellen J. Zucker, a Boston lawyer who argued before her on multiple occasions. "But she had, in my experience, a narrower view of what the legal system could accomplish and what it is obliged to accomplish to secure people's rights. That said, I had enormous respect for her."
Justice Sosman argued for civil unions instead of gay marriage, calling the issue "a squabble over the names to be used."
"What's in a name? That which we call a rose, By any other name would smell as sweet," she wrote, quoting Shakespeare's "Romeo and Juliet."
In the majority opinion, Marshall said Justice Sosman "so clearly misses the point that further discussion appears to be useless."
Over the past two years, while undergoing chemotherapy and radiation treatment, she continued to take part in oral arguments, sitting on the bench as recently as February. "She was fully prepared and asked wonderful questions as always," Marshall said. "She demonstrated her commitment to the work of the court throughout this challenging illness."
She used e-mail, faxes, the phone, and even monitored arguments over the Web when she couldn't attend.
"The loss feels so enormous, because she's been such an active colleague," Marshall said. "It's an enormous void."
Justice Sosman leaves her father, J. Leland of Concord; a brother, Eric of Newton; and three sisters, Nancy of Sebago, Maine, Carol Sosman Ham of Mansfield, and Amy of Portsmouth, N.H.
Funeral arrangements were pending last night.