Martha B. Sosman, one of three Massachusetts Supreme Judicial Court judges who voted against the landmark decision legalizing gay marriage in the state, has died, the court said Sunday. She was 56.

Sosman was diagnosed with breast cancer in 2005 and had been participating in some cases by watching Webcasts of oral arguments, reading legal briefs at home and talking with other justices and law clerks by telephone.

Republican Gov. Paul Cellucci hailed Sosman as a "conservative" jurist when he appointed her to the high court as an associate justice in 2000.

She said the argument to define gay partnerships as marriages versus civil unions was "a squabble over the names to be used."

Sosman was a former assistant U.S. attorney in Massachusetts and founded an all-women law firm in 1989, where she worked until she was appointed to the Superior Court in 1993.