Disposing of a constitutional challenge to the federal sentencing system (search), the Supreme Court has set up an anticipated fight in Congress over how judges punish convicted criminals.

The court on Wednesday struck down part of the nearly two-decade-old sentencing system, then imposed new requirements that were contested even among the justices.

Justice Antonin Scalia (search) predicted that changes would "wreak havoc on federal district and appellate courts." Justice John Paul Stevens (search) said that his colleagues "erased the heart" of reforms intended to ensure that sentences do not vary widely from courtroom to another.

The Supreme Court had spent the past four months trying to reconcile a defendants' constitutional right to a jury trial with a system that requires judges to make factual decisions that affect prison time.

Juries consider a person's guilt or innocence. Judges decide matters such as the amount of drugs involved in a crime or the number of victims in a fraud. Those factors are used, under the federal guidelines, to add years to someone's sentence.

More than 60,000 defendants are sentenced each year in federal courts.

In a compromise, the court decided that judges should consult the guidelines in determining sentences - but only on an advisory basis. Appeals courts must ensure that sentences are reasonable.

"Ours, of course, is not the last word. The ball now lies in Congress' court," Justice Stephen Breyer (search) wrote in one part of the ruling.

The decision did not spell out how judges should deal with defendants or what options Congress has.

"The remedy the court has adopted will add to the mess," said Douglas Berman, an Ohio State University sentencing expert.

Justice Department lawyer Christopher Wray said the guidelines have ensured that "similar defendants who commit similar crimes receive similar sentences. Because the guidelines are now advisory, the risk increases that sentences across the country will become wildly inconsistent."

Senate Judiciary Chairman Arlen Specter, R-Pa., said he would begin working to "establish a sentencing method that will be appropriately tough on career criminals, fair, and consistent with constitutional requirements."

Sen. Patrick Leahy of Vermont, ranking Democrat on the Judiciary Committee, warned that Congress "should resist the urge to rush in with quick fixes that would only generate more uncertainty and litigation and do nothing to protect public safety."

Wednesday's ruling had two parts.

In the first, a coalition of liberal and conservative justices said the practice of judges' acting alone to decide factors that add prison time violates a defendant's Sixth Amendment (search) right to a jury trial.

That same combination of justices held sway in June in a state sentencing case that led to the much-anticipated ruling on federal sentences: Scalia, Stevens and Justices Clarence Thomas (search), David H. Souter (search) and Ruth Bader Ginsburg (search).

Ginsburg switched sides in the accompanying vote to make the guidelines voluntary, joining fellow Clinton appointee Breyer along with Chief Justice William H. Rehnquist (search) and Justices Sandra Day O'Connor (search) and Anthony Kennedy (search).

Rehnquist, who has been absent from the bench since October while being treated for thyroid cancer, participated but did not write any of the opinions.

"I had hoped for a little bit more clarity, but I'm not terribly surprised," said Jeffrey Fisher, a Seattle lawyer who argued last year's sentencing case. "We don't have a crippled system that will not work."

Judges will have more freedom to decide for themselves what a fair sentence is, without making factual findings that the high court objected to. That flexibility may benefit prosecutors in some courts and defendants in others, Fisher said.

The cases are United States v. Booker, 04-104, and United States v. Fanfan, 04-105.