Judge Betty Binns Fletcher, considered a liberal stalwart of the 9th U.S. Circuit Court of Appeals for decades, has died at age 89, a spokesman for the court said Tuesday.

Fletcher passed away Monday night. The cause was not immediately known, 9th Circuit spokesman David Madden said.

Appointed to the bench by President Jimmy Carter in 1979, she was known for rulings upholding affirmative action, allowing claims of workplace discrimination to proceed, overturning death penalty cases and protecting the environment. She was one of the first female partners at a major law firm in the country, and the second woman appointed to the 9th Circuit.

"She had experienced discrimination herself in her life, and her perspective included looking out for the downtrodden, the little person — but always within the framework of the law," Seattle U.S. District Judge Robert Lasnik said.

Fletcher kept hearing cases until the end, he added, and she remained sharp even as her body failed her.

Many of Fletcher's favorite opinions were overturned by an increasingly conservative U.S. Supreme Court, her son, 9th Circuit Judge William A. Fletcher, wrote in a 2010 tribute. He called it her "distinguished record of reversals."