WASHINGTON — A federal appeals court has identified the three judges who will decide whether a former White House aide sentenced to 2 1/2 years in prison on obstruction of justice charges, I. Lewis Libby Jr., must report to prison immediately or can avoid jail-time until his appeals are exhausted.

The panel contains one judge considered an ardent conservative, David Sentelle, and another considered somewhat liberal, David Tatel. A swing vote in the case involving the former chief of staff to Vice President Cheney could come from the third judge, Karen Henderson.

“She’s a balanced jurist for the most part. I don’t think she’s a strident partisan by any stretch of the imagination,” an attorney and political science professor who has studied the political leanings of the court, Christopher Banks of Kent State University, said.

Judge Sentelle was appointed to the appeals court by President Reagan, Judge Tatel by President Clinton, and Judge Henderson by President George H.W. Bush.

Mr. Banks said the political impact of the case is likely to be less of factor than the court’s unreceptive attitude to most appeals by criminal defendants. The judges “tend to be very deferential especially in criminal matters, unless there’s an egregious error,” the professor said.

“I think big ‘P’ politics will come out in the wash, and it will turn on jurisprudential views,” a lawyer who practices regularly before the court, Erik Jaffe, said. He said all the judges are reluctant to overturn the rulings of district court judges, such as Judge Reggie Walton, who has denied Libby a stay of his sentence.

If the appeals judges stay Libby’s sentence, President Bush will get a reprieve from having to make a decision about a possible pardon for the former aide. If Libby is ordered to jail, Mr. Bush is expected to be pressured to act immediately.