WASHINGTON — In a day punctuated by flashes of hostility and humor, Judge John G. Roberts Jr. on Tuesday acknowledged a constitutional right to privacy and said overturning precedent was a "jolt to the legal system."

But he artfully sidestepped the hot-button question that has dogged him as a Supreme Court nominee: whether he opposes Roe v. Wade, the 1973 decision that legalized abortion.

Roe became an issue minutes after the start of the second day of the first Supreme Court confirmation hearing in 11 years, a day in which Roberts, President Bush's nominee to be the nation's 17th chief justice, was also grilled on his views on civil rights, gender discrimination, presidential authority and the proper role of judges.

Sen. Arlen Specter, R-Pa., chairman of the Senate Judiciary Committee, asked Roberts a series of questions intended to draw him out on whether he believes the right to abortion is so embedded in the fabric of American life that it must not be overturned.

The nominee wasted little time in drawing the line against answering questions that, he said, could come before the court. Four minutes into the hearing, he told Specter, "I feel the need to stay away from a discussion of particular cases."

He reiterated that phrase in one form or another throughout the day on subjects as varied as the right to die and the treatment of foreign detainees.

Roberts told the senators that he did not have a specific legal philosophy, and he resisted comparisons to William H. Rehnquist, the late chief justice for whom he once clerked, telling senators that he would be "my own man."

He also flatly rejected the idea that his Roman Catholic religion played a role in his judging, saying: "I look to the law books and always have. I don't look to the Bible or any other religious source."

The session, which began at 9:30 a.m. and continued late into the day, was the Judiciary Committee's first unscripted public exchange with Roberts. It offered Senate Democrats, who have complained bitterly that they know too little about the nominee's personal views, their first chance to question Roberts on his judicial philosophy and legal record.

Drawing on thousands of documents from the nominee's days as a young lawyer with the Reagan administration, the Democrats peppered Roberts with questions on presidential authority, civil rights and gender discrimination. In response, the nominee often emphasized that his positions then were those of his supervisors, as opposed to his own.

Toward the end of the day, both sides could barely contain their exasperation.