At her confirmation hearings in 1981, Sandra Day O'Connor was asked what kind of legacy she'd like to leave. "Ah, the tombstone question," she said. "I hope it says, 'Here lies a good judge.'"

Almost no one thought she was a good judge on every decision, of course, but she certainly was an interesting one. She will be remembered as a centrist, but it's more accurate to say she came down sometimes on the right and sometimes on the left.

O'Connor's early life provides few clues to those hoping to pin down her judicial philosophy. She grew up on a ranch in southeastern Arizona. By age 8, she could rope, ride and repair fences with the ranch's cowboys, shoot a .22 and drive a pickup truck.

Yet her mother read to her daily from The Wall Street Journal, the Los Angeles Times, the New Yorker and the Saturday Evening Post. She spent school years with her grandmother in El Paso so she could attend an exclusive all-girls private academy.

It was a dichotomy of experience that would inform the rest of her life -- through Stanford University law school, the Arizona legislature and even her Supreme Court tenure. She was basically conservative, yet supported causes such as the Equal Rights Amendment. She battled discrimination, yet wrote that government programs that set aside a fixed percentage of public contracts for minority businesses violate the Constitution's equal protection clause.

Conservatives loved her parting shot, a seething dissent in the Kelo v. New London case. Her spirited defense of property rights -- a hallmark of her jurisprudence dating back to her earliest days on the Arizona Court of Appeals -- in a 5-4 case could well provide the legal bedrock for overturning Kelo in the future.

They were less fond of her joining the majority in Lawrence v. Texas to strike down the Lone Star State's sodomy law or her decisions in the recent Ten Commandments cases, in which she came down against public display of the rules on which our legal system is built.

Conservatives were equal measures perplexed and apoplectic at the reasoning of her decisions in Gratz and Grutter -- the twin cases concerning University of Michigan's minority-preference admissions practices. Her legal reasoning, she said in one of the decisions, hopefully wouldn't hold up in 25 years. How can this be, conservatives asked -- will the Constitution read differently in 25 years? Will the principles that should underlie such decisions (or at least ought to) have changed?

But if the decisions threw the right for a loop, the unpredictability of their author shouldn't have. She graduated third in the class of 1952 at Stanford Law School; William Rehnquist, now chief justice, finished first. Thus, when she was appointed to the court, she was regarded as so conservative that Time Magazine labeled her Justice Rehnquist's "Arizona twin." Yet a Democratic governor had appointed her to Arizona's state senate, and she rose to majority leader with a moderate voting record.

In her Senate confirmation hearings, she refused to be pinned down on abortion. She was approved 99-0 with one senator voting "present" because she refused to condemn Roe v. Wade.
No sooner was O'Connor sworn in than she joined the liberal wing in a 5-4 ruling that a state-supported university in Mississippi could not exclude men from its school of nursing.
Her ideological bedfellow turned out not to be Rehnquist but centrist Lewis Powell. They came down on the same side of more 5-4 decisions than any other two justices. When David Souter, another Republican appointee who turned out not to be as conservative as hoped, joined the court, he and O'Connor were on the same side of every 5-4 decision during his first term.

And when she did side with conservatives, she often wrote her own concurrence, which usually limited the reach of the opinion.

For example, a concurrence she wrote in Lynch v. Donnelly, a 1984 case on the constitutionality of a government-sponsored nativity scene, has established the legal standard for when such displays violate the Constitution's prohibition on government establishment of religion. The next year, her concurrence essentially outlined the constitutional bounds on a state-prescribed "voluntary moment of silence" for school children. O'Connor wrote that the challenged law was unconstitutional because it encouraged prayer but might have been acceptable had it not favored "the child who chooses to pray over the child over chooses to meditate or reflect."

A "good judge"? The jury's still out. But O'Connor kept things lively -- for both the right and the left.

Paul Rosenzweig is a senior fellow in the Heritage Foundation Center for Legal and Judicial Studies and a former Justice Department lawyer.