U.S. Supreme Court nominee John Roberts will be grilled on matters from abortion to civil rights when his Senate confirmation hearing opens, but a key issue is how much the 50-year-old conservative will answer.

Getting responses from Roberts on where he stands on issues may be Democrats? only hope of blocking what opponents view as a move by President George W. Bush to shift the nation?s top court to the right.

If confirmed, Roberts, a federal appeals judge, will replace retiring Justice Sandra Day O?Connor, a mainstream conservative who often cast the decisive vote on the closely divided court.

?Federal court candidates, who serve for life, should explain their judicial philosophy and their method of legal reasoning?, said Sen. Charles Schumer, a New York Democrat and Senate Judiciary Committee member who has already given Roberts a seven-page list of questions.

Key to the process will be committee Chairman Sen. Arlen Specter, a moderate Republican who will run the televised hearings that begin Sept. 6. He wrote in his 2000 book ?Passion for Truth? that ?the Senate should resist, if not refuse, to confirm Supreme Court nominees who refuse to answer questions on fundamental issues?. Sen. Orrin Hatch, a Utah Republican and former chairman of the committee, said panel members can ask what they want. ?But we must realize, as we have in the past, that simply asking a question does not mean a judicial nominee should answer it?, he said. Republicans also contend Roberts should not have to prejudge any case that could come before him. That means he could refuse to answer many questions.

The nation?s top court deals with virtually every major issue affecting Americans, from terrorism and church-state disputes to the balance of power between the federal and state governments.

While no Democrats have announced plans to oppose him, they want to know where Roberts, who served in the administrations of two previous Republican presidents, stands on some landmark Supreme Court rulings such as the 1973 Roe v. Wade decision that legalized abortion.

Democrats have also demanded access to internal documents on Roberts relating to divisive issues including school desegregation, the death penalty and civil rights. The Justice Department on Friday refused to release some of the requested documents from Roberts? work for the agency, saying it was not in the public interest.

Volokh said an exception to the pattern of nominees not answering questions was Robert Bork, ?who answered questions in great detail and got rejected.? Bork was nominated in 1987 by Republican President Ronald Reagan and viewed by critics as a conservative extremist.

Specter, not chairman at the time, opposed Bork, saying, ?I believe there is substantial doubt as to how he would apply fundamental principles of constitutional law.?

<B>Thomas FERRARO</B>