The court, on a 5-4 vote, said that its ruling last June that juries — not judges — should consider factors that can add years to defendants' prison sentences applies as well to the 17-year-old federal guideline system.
The justices refused to backtrack from the 5-4 decision that struck down a state sentencing system because it gave judges too much leeway in sentencing. But the high court stopped short of striking down the federal system.
"This is a huge blow to the federal sentencing guidelines and really to any state sentencing guidelines that allow judges to increase sentences based upon facts that a jury did not hear," said CBS News Legal Analyst Andrew Cohen.
"The court didn't outright strike down the federal sentencing guidelines but clearly those rules now are in jeopardy," Cohen said.
Assistant Attorney General Chris Wray with the Department of Justice said he was pleased that the guidelines were not completely eliminated, but said making them "advisory in nature" poses the risk of sentences becoming "wildly inconsistent."
"The guidelines are as important as anything we do," Wray said. "Nothing is more important than our sentencing regime."
Justice Stephen Breyer said the federal sentencing system is at least in part invalid because it forces judges to be driven by the guidelines. But he said that the system could be salvaged, if judges use it on an advisory basis.
Justice Antonin Scalia said that solution would "wreak havoc on federal district and appellate courts quite needlessly, and for the indefinite future."
About 64,000 people are sentenced in federal courts each year, under a system that had been challenged as unconstitutional in a pair of cases at the Supreme Court.
The divided ruling Wednesday took longer than expected. Justices had put the issue on a fast track, scheduling special arguments on the first day of their nine-month term in October. Most court watchers expected a ruling before the holidays.
The federal guidelines are intended to make sure sentences do not vary widely from courtroom-to-courtroom. While juries consider guilt or innocence, judges make factual decisions that affect prison time, such as the amount of drugs involved in a crime, the number of victims in a fraud or whether a defendant committed perjury during trial.
The high court's vote that federal defendants were entitled to jury judgments was 5-4 and included the same odd right-left combination of justices as those who had held sway in June. Scalia and Justice Clarence Thomas are the court's most conservative members. Justices John Paul Stevens, David H. Souter, and Ruth Bader Ginsburg are in the liberal wing.
In a dissent, the other four justices wrote: "history does not support a `right to jury trial' in respect to sentencing facts." Those four are Chief Justice William H. Rehnquist and Justices Sandra Day O'Connor, Anthony Kennedy and Breyer.
A different coalition of justices, led by Breyer, voted to allow the sentencing guidelines to stand, but not force judges to use them.
"We're disappointed in the ruling and we are currently reviewing it. We will have more to say later," said Justice Department spokesman Mark Corallo.
The federal guidelines were being contested in two cases involving men convicted on drug charges in Wisconsin and Maine.
Justices, in siding with one of the men, opened the door to thousands of claims by other defendants. Stevens said that not all of them will get new sentencing hearings. Judges must sort through the claims, he said, to determine which defendants have current appeals on the subject.
Defense lawyers and prosecutors had been anxiously awaiting the ruling.
"The whole federal criminal law system is operating in a state of suspended animation," said Jeffrey Fisher, a Seattle attorney who argued last year's sentencing case. People have been waiting "for the shoe to drop so we can start grappling with the hard issues in the aftermath."
The cases are United States v. Booker, 04-104, and United States v. Fanfan, 04-105.