WASHINGTON - In a portent of the potential battle this summer over the Supreme Court, Goodwin Liu, President Obama's choice for the San Francisco-based U.S. Court of Appeals for the Ninth Circuit, faced a fusillade of criticism Friday from Senate Republicans, who questioned his fitness for the bench.

Liu, 39, a law professor at the University of California, Berkeley, is considered among the most liberal of Obama's judicial nominees. While Republicans appear poised to oppose him, they are also using his nomination to telegraph their concerns about Obama's impending Supreme Court pick.

Sen. Jeff Sessions of Alabama, the top Republican on the Senate Judiciary Committee, called Liu "the very vanguard of what I would call an intellectual judicial activist."

The GOP views Liu's nomination as part of a larger struggle over the direction of the federal judiciary, and senators Friday repeatedly suggested Liu would "create" or "invent" new rights under the Constitution or apply the law in a biased manner.

Their arguments echoed many criticisms directed at Justice Sonia Sotomayor during her Supreme Court confirmation hearing last year.

Republicans also pointed to Liu's lack of judicial experience. He has never been a judge and has argued few cases in court. Democrats, conversely, praised Liu's credentials and background as unassailable - and pointed out that two dozen Bush administration nominees similarly had never been judges.

Liu is a child of Taiwanese immigrants, a former Rhodes scholar with an undergraduate degree from Stanford University and a law degree from Yale University.

Liu, like Sotomayor last year, portrayed himself as bound by judicial precedent - rulings in previous cases - and said there was no room for a judge to insert personal views into a case. "I would approach every case with an open mind," he told the committee. "The role of a judge is to faithfully follow the law as it is written."

Liu struggled to reconcile some of the policy positions in his academic writings with that role. He has criticized conservative legal doctrine, written that interpretation of the Constitution must evolve and adapt to a changing society, and theorized that people may have a constitutional right to "welfare" benefits, such as education and shelter, if those things are bestowed upon them by legislative action.

"Whatever I may have written in books or in articles would have no bearing on my role as a judge," Liu said.

"How can you say that?" Sessions interjected.

Sen. Jon Kyl (R., Ariz.) unleashed the most vitriolic attack on Liu in addressing the nominee's criticism of Justice Samuel A. Alito Jr.

Liu testified before the Judiciary Committee in 2006 in opposition to Alito's confirmation. He said then: "Judge Alito's record envisions an America where police may shoot and kill an unarmed boy to stop him from running away with a stolen purse, ... where a black man may be sentenced to death by an all-white jury for killing a white man. I humbly submit that this is not the America we know. Nor is it the America we aspire to be."

Kyl called Liu's remarks "vicious, emotionally and racially charged, very intemperate," and said they called into question Liu's capacity for fairness.

Senate Judiciary Chairman Patrick J. Leahy (D., Vt.) called Kyl's criticism "outrageous." Liu conceded he had used overly "colorful language" in his testimony.

During a break in the hearing, Sessions said he remained troubled by Liu's nomination. "I haven't seen anything that's made me feel any better," he said.

The hearing was dominated by Republicans, but they ultimately hold little sway on a committee where Democrats outnumber them, 12-7. That means Liu is likely to receive its stamp of approval as early as next month.

But Democrats would likely need 60 votes to move Liu's nomination to a floor vote, and the conflict could consume substantial time on a crowded Senate calendar.