A possible revolution in the federal criminal justice system will be on the agenda when the Supreme Court opens its new term tomorrow.

In a rare two-hour afternoon oral argument session, the justices will consider whether the federal sentencing guidelines -- a manual of 400-plus pages meant to ensure that federal courts give defendants across the country approximately equal punishments for similar crimes -- can be reconciled with the Constitution.

The court is hearing the case on an expedited schedule in response to the uproar and confusion created by a 5 to 4 ruling it issued June 24, just before leaving for summer recess.

In that case, Blakely v. Washington, the court struck down Washington state's sentencing guidelines, which, like the federal guidelines, permit judges to boost sentences based on their own post-conviction fact-finding, rather than relying only on facts admitted by the defendant or found by a jury.

That, the court ruled, violates the right to a jury trial guaranteed by the Sixth Amendment.

Though the court said in Blakely that it did not address the federal guidelines, the similarities between Washington's system and the federal system were such that defense lawyers across the country immediately began bombarding courts with Blakely challenges to their clients' sentences.

Lower courts have issued differing rulings in response, and some federal prosecutors have felt obliged to redraft indictments to make sure they conform to Blakely.

"It looks like a Number 10 earthquake to me," Justice Sandra Day O'Connor, who dissented in Blakely, told a conference of federal judges in July.

Although determining the precise magnitude of the Blakely aftershocks is the court's first major item of business, Blakely is by no means the only case of potential national significance on the court's docket.

On Oct. 13, the court will hear arguments in Roper v. Simmons, No. 03-633, a challenge to the constitutionality of the death penalty for persons who commit crimes while younger than 18.

The court has barred capital punishment for those younger than 16, but it ruled in 1989 that capital punishment for 16- and 17-year-old defendants does not constitute "cruel and unusual punishment."

However, the court may decide that a "national consensus" has now formed against imposing the ultimate penalty against minors -- just as it did in 2002 with respect to the death penalty for moderately mentally retarded offenders.

It is nearly certain that the court's two swing voters, Justices O'Connor and Anthony M. Kennedy, will determine the outcome. Four members of the court -- John Paul Stevens, David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer -- have already declared in a published opinion that they believe the death penalty for juveniles should be abolished.

Chief Justice William H. Rehnquist and Justices Antonin Scalia and Clarence Thomas opposed the 2002 mental retardation ruling, which opponents of capital punishment for juveniles are relying on to make their case.

In Ashcroft v. Raich, 03-1454, the court will determine whether the federal government has the power to outlaw the personal cultivation and use of marijuana for medicinal purposes, even when the marijuana stays in a user's home and never crosses state lines.

Angel McClary Raich is a brain tumor patient in California whose doctor advised her to smoke marijuana for pain relief. This is permissible under a 1996 California law, but federal agents have arrested medical marijuana users. So Raich joined a lawsuit in October 2002, asking a court to bar Attorney General John D. Ashcroft from enforcing federal drug laws against her.

The U.S. Court of Appeals for the 9th Circuit, based in San Francisco, sided with Raich last year, ruling that the federal government cannot punish drug use that does not affect interstate commerce.

The Bush administration appealed to the Supreme Court, arguing that an exemption for personal use or free distribution would discourage the consumption of lawful pain medicines and thwart Congress's intent to regulate the drug market comprehensively.

In addition, the court will decide in two consolidated cases whether some states may ban the direct shipment of wine from other states.

The cases, Granholm v. Heald, No. 03-1116, and Swedenburg v. Kelly, No. 03-1274, pit winemakers eager to sell on the Internet against state governments that say they will see a surge in underage drinking and a loss in tax revenue if wine no longer goes through licensed, in-state wholesalers.

Proponents of direct shipment say that states such as Michigan and New York are using such arguments to protect local wineries, and that their laws violate the Constitution's implicit prohibition against state trade barriers.

But the states say their authority comes from the 21st Amendment, which repealed Prohibition in 1933. It bars the importation of alcohol into any state "in violation of the laws thereof."

Neither the wine cases nor the medical marijuana case has been scheduled for argument yet.

The case to be argued tomorrow has its roots in a sentencing reform movement that emerged after a 1972 report by federal Judge Marvin E. Frankel decried the "almost wholly unchecked and sweeping" power of judges to set sentences.

In 1984, Congress established the United States Sentencing Commission as an independent agency within the judicial branch. The commission's first set of guidelines took effect in 1987 and survived a Supreme Court test unrelated to the Sixth Amendment in 1989. The judges and other experts who make up the seven-member panel amend the guidelines each year, after Congress has had 180 days to veto any proposed changes.

Under the guidelines, judges are given a variety of factors to consider in deciding how harshly to punish within the range of penalties established by law.

In a typical case, such as one before the court now, U.S. v. Booker, No. 04-104, an accused drug trafficker either pleads guilty or is convicted by a jury of selling cocaine, and then a government probation officer presents the judge with findings as to the exact amount of drugs involved.

A jury found that Freddie Booker had trafficked more than 50 grams of cocaine. The judge found that the actual amount was 658.5 grams, that Booker had perjured himself at trial and that he had 23 prior convictions. The result under the guidelines: a sentence of 30 years, far longer than Booker would have gotten for trafficking 50 grams.

Though judges increasingly complain that the guidelines limit their ability to tailor justice to individual cases, they have largely cured the inequities that Frankel identified.

But in 2000, the Supreme Court decided Apprendi v. New Jersey, in which the court struck down a 12-year state sentence for a gun crime because it had been increased from 10 years based only on a judge's finding that the crime had been motivated by racial bias.

Other than the fact of a prior conviction, a five-member majority of the court announced in an opinion by Stevens, "any fact that increases the penalty for a crime beyond the prescribed statutory maximum must be submitted to a jury, and proved beyond a reasonable doubt."

At the time, Breyer, who played a role in developing the guidelines as a Senate aide and federal appeals judge, predicted that Apprendi would destroy them. And with the liberal-conservative alliance on the court that voted for Apprendi -- Stevens, Scalia, Souter, Thomas and Ginsburg -- sticking together in Blakely, that prediction came true.

While Breyer, O'Connor and others protest that Blakely's benefit to defendants is far outweighed by the cost in legal disruption, opponents of the guidelines insist that whatever equity in sentencing they achieved was at the expense of defendants' right to face a jury of their peers.

Judges must only conclude that sentencing "factors" have been proved by a preponderance of the evidence, rather than the jury's tougher "beyond a reasonable doubt" standard.

This unduly increases the leverage of prosecutors, defense attorneys argue, giving them the upper hand in plea negotiations, through which about 97 percent of the 65,000 federal convictions in fiscal 2002 were achieved. In their view, the ultimate impact of Blakely will simply be a shift in favor of defendants during plea bargaining.

"Given past experience, there is no reason to believe that Blakely-specific indictments will cause an increase -- much less a catastrophic increase -- in trials," the National Association of Federal Defenders told the court in a friend-of-the-court brief. "Rather, the more specific allegations give the parties specific details with which to reach successful compromise and negotiations."

But, in its brief defending the guidelines, the Bush administration argues that Blakely should not apply to the federal guidelines because, unlike the Washington state guidelines, they were created not directly by statute but by a commission within the judicial branch.

The commission's work is "the accumulated judicial wisdom about the facts that matter at sentencing," the brief notes.

If the court throws out the guidelines, the issue will return to Congress. Early congressional reactions to Blakely suggest that the ultimate result of scrapping the guidelines would be harsher penalties prescribed by politicians reluctant to be seen as soft on crime.

"[I]t may take only a couple of lenient sentences in high-profile cases to raise enough of a stir to increase mandatory minimum penalties," Sen. Orrin G. Hatch (R-Utah) said at a July 13 hearing of the Senate Judiciary Committee.