WASHINGTON (AP) _ Chief Justice William H. Rehnquist might accomplish a first today, presiding over the Supreme Court and President Clinton's impeachment trial, then attending the president's State of the Union address.

The chief justice presided over the Supreme Court's regularly scheduled session this morning as the court issued orders and heard oral arguments.

Rehnquist appeared testy at times during arguments in a Pennsylvania case. At one point, he told a lawyer, ``You've been asked several questions. Try to answer the question.''

In the afternoon, he was crossing the street to oversee the day's impeachment trial proceedings in the Capitol's Senate chamber.

In the evening, Rehnquist can complete the triple-header by attending Clinton's annual State of the Union address before a joint session of Congress in the House chamber.

Supreme Court justices traditionally sit on the front row in their judicial robes, remaining silent as various members of Congress interrupt the president's speech with applause or cheers.

However, not all of the justices attend every time, and it was possible Rehnquist would stay away to avoid any appearance of a conflict because of his role in the impeachment trial.

Rehnquist, an amateur artist, once skipped the president's address to attend the first night of an adult-education painting class in suburban Arlington County. That happened in 1984, two years before he was elevated to chief justice.

Court spokeswoman Kathy Arberg declined comment Monday on whether the chief justice planned to attend the president's address. The court typically does not announce in advance which justices will attend a State of the Union speech.

The only other chief justice to preside over a presidential impeachment trial was Chief Justice Salmon Chase, who oversaw the 1868 trial in which President Andrew Johnson was acquitted by one vote. Presidents sent their State of the Union messages to Congress in written form at that time, and Johnson delivered his message months before the trial.