Supreme Court nominee Sonia Sotomayor appeared headed toward US Senate approval, but the first Hispanic high court nominee offered few clues on how she would rule once seated on the court.

In the past, liberal jurists have become conservatives on the court and vice versa -- at least on some key issues, including abortion, gays rights and civil rights.

With Democrats in control of the Senate, a vote on President Barack Obama's first Supreme Court nominee was expected by Thursday, but if past is precedent it may take years to determine what sort of justice she will be.

"There's no way you can tell," Senate Judiciary Committee Chairman Patrick Leahy, a Democrat and Sotomayor backer, told Reuters. "Judges can change during their lifetime appointments," Leahy explained.

Consider former Chief Justice Earl Warren, appointed in 1953 by Republican President Dwight Eisenhower. Warren became a liberal lion on the court and Eisenhower called the appointment "the biggest damned-fool mistake I ever made."

President John Kennedy never made such pronouncements, at least publicly, about Byron White, who he appointed to the court in 1962. But many Kennedy backers were disappointed White was less liberal and more conservative than expected.

But Souter ended up on the liberal wing of what has been a sharply divided court, one that in recent years has routinely ruled 5-4 in favor of conservatives.

Republican Senator Lindsey Graham, an early critic, announced last month he would vote to confirm Sotomayor but also voiced uncertainty.

'TIME WILL TELL

"I think that Judge Sotomayor will not be any more liberal than him (Souter), and on some issues, quite frankly, may be more balanced," Graham said. "Time will tell."
Harry Blackmun, a 1970 appointee of President Richard Nixon, was expected to be a conservative justice. Yet he wrote the 1973 Supreme Court ruling that legalized abortion and still riles Republicans. He also reversed himself and opposed the death penalty.

"I assume Nixon regretted the pick," said Jamal Greene, a professor at Columbia Law School who clerked in 2006 and 2007 for Supreme Court Justice John Paul Stevens.
Stevens was appointed in 1975 by Republican President Gerald Ford. He was then seen as a moderate but emerged as a liberal on the high court.

"He says he hasn't changed, but that the court moved to the right on him," said Greene. At 89, Stevens, remains a maverick justice and a thorn in the side of conservatives.
Current members of the Court have for the most part performed as expected as the Senate confirmation process has become tougher over the last 50 years, Greene said.

He said Souter had been "the biggest surprise by far, adding that Anthony Kennedy, another Republican appointee, had been more liberal on at least some issues, including gay rights and the death penalty, than expected.

Republican Leader Mitch McConnell and Senate Democratic Leader Harry Reid raised the curtain on the Sotomayor debate.

McConnell said he opposed Sotomayor largely because of what he said was Obama's focus on empathy in looking for a justice.

"Empathy is only good if you're lucky enough to be the person or the group that the judge in question has empathy for," McConnell said.

Reid brushed off such talk and made a prediction about the first Hispanic Supreme Court nominee. "This week the Senate will make history when we confirm her."