Sears, 53, who has served on the Georgia Supreme Court since 1992, said she worried she would fall into a "rut" if she continued. She said she will instead seek jobs in the private sector, perhaps as a university president or at a civil rights law firm.
"It was time to turn a new page, to start a new adventure," she said in an interview. "I have truly loved this job and I loved being chief justice, but it's time to move on and let the institution carry on. And I think I've made the contribution I've wanted to make."
But Sears, who has been mentioned as a potential U.S. Supreme Court nominee, did not rule out an eventual return to the public sector.
"I'd like to expand my wings a little bit," she said. "I haven't ruled out, 100 percent, another elected or appointed office. But perhaps for the short term, that wouldn't be a wise thing to do."
Sears began her career as a jurist in 1985 at the age of 27, when she was appointed to Atlanta's traffic court. Three years later, she became the first black Superior Court judge in Georgia.
She broke another barrier in 1992 when Gov. Zell Miller appointed her to the Georgia Supreme Court, making Sears the youngest person to ever serve on the court.
"I admire the chutzpah I had for being able to come in here when the average age of the judges was something like 62 and I was walking around here at 36," she said with a laugh.
She won re-election three times, becoming the first woman to win statewide election in Georgia. In her third election victory in 2004, widely seen as a referendum on whether Sears should become head of the court, she won by more than 300,000 votes.
"To break down the stereotypes that Georgia is somehow a backwater state that would never elect an African-American, a woman, or an African-American woman to chief justice is one of my proudest accomplishments," she said.
She's won accolades for presiding over one of the more productive state appellate courts in the nation. She also has lobbied legislators for increased judicial funding and more support for a statewide public defender system.
Since Sears became chief in 2005, her court has been at the heart of several controversial decisions, including a high-profile ruling that freed Genarlow Wilson, who was serving a mandatory 10-year sentence for having oral sex with a 15-year-old when he was 17.
The court also has been scrutinized for its long-standing practice of reviewing death penalty cases to determine if the punishment is proportional to the crime. U.S. Supreme Court Justice John Paul Stevens criticized the review in an opinion this month as "utterly perfunctory."
Her role as Georgia's chief has earned her national attention, and at speaking events she is routinely introduced as a potential Supreme Court nominee if Barack Obama wins the presidential election. She has refused to speculate, though, and said she is focusing on her next step.
"I'm going on with my plans, building my own bridge to what I want to do next. You never know what may happen, and I'm open to all kinds of possibilities. But I don't think you just sit around and wait for things to go your way."