ASHINGTON, Oct. 3 - The Supreme Court opens its new term on Monday faced with urgent business and looming uncertainty.

The justices' most pressing task is to resolve the fate of the federal criminal sentencing system, which the court itself threw into limbo in June by declaring unconstitutional a similar, although not identical, system used by the state of Washington.

In both the state and federal systems, sentencing guidelines provide a starting point for calculating a criminal sentence, and judges then make findings about a variety of factors to determine how much time a defendant will actually serve. The Supreme Court held in Blakely v. Washington that the state system violated the constitutional right to trial by jury by permitting judges to make these essential findings.

Federal judges around the country quickly started ruling that they could no longer treat the federal sentencing guidelines as binding. Whether that judgment is correct and, if so, what should happen next will be the subject of an unusual afternoon argument on Monday in two cases that the justices granted in August at the Justice Department's request and agreed to expedite for an argument that would not ordinarily have been scheduled until January.

The uncertainty as the term begins derives not from a particular case but from the calendar. It has been more than 10 years since a justice retired, making this the longest-serving Supreme Court since the 1820's. And with institutional longevity, of course, comes age: Justice David H. Souter's 65th birthday last month left Justice Clarence Thomas, 56, the only member of the court who is under 65.

Chief Justice William H. Rehnquist turned 80 on Friday. His intentions, like those of his colleagues, remain opaque even as the presidential campaign shines an election-year spotlight on the court and its future.

The justices have accepted 49 cases for review so far, enough to fill their argument calendar into early February and leaving room for perhaps two dozen more to be accepted over the coming weeks in time to be decided during the new term.

While the sentencing cases alone - United States v. Booker, No. 04-104, and United States v. Fanfan, No. 04-105 - would mark this as an unusually important term for criminal law, the justices have also agreed to decide a significant death penalty case. The question in Roper v. Simmons, No. 03-633, is whether executing someone convicted of committing a capital murder at the age of 16 or 17 offends "evolving standards of decency in a civilized society." That is the test the court applies to decide whether a punishment is "cruel and unusual" within the meaning of the Eighth Amendment.

In 1988, the court prohibited the execution of those whose crimes were committed at 15 or younger, but refused the next year to extend that decision to 16- and 17-year-olds. Although there have been few executions for juvenile crimes in recent years, the United States is one of only a handful of nations where such executions are still possible, and the case has attracted worldwide attention. Seventy-three people are currently on death row in 12 states, one-third of them in Texas, for crimes committed before the age of 18.

Following are some of the other important cases the court has agreed so far to hear during its new term:

Criminal Law

It is a new twist on a familiar question: what investigatory techniques can the police use once they have stopped a motorist for a routine traffic violation? In this case from Illinois, the question is whether, without any particular reason for suspicion, the police can subject the stopped car to an inspection by a trained drug-sniffing dog. The Illinois Supreme Court held that use of the dog, which detected a trunk full of marijuana, violated the Fourth Amendment by impermissibly broadening the scope of a routine traffic search. The state's appeal is Illinois v. Caballes, No. 03-923.

Federalism

The justices' continuing re-examination of the boundaries between national and state authority can sometimes appear rather abstract and academic, but not this year. The court's two federalism cases are both likely to generate interest and attention. In one, the Bush administration is defending federal narcotics enforcement authority over the medical use of marijuana in states that have authorized use of the drug for that purpose.

The United States Court of Appeals for the Ninth Circuit, in San Francisco, ruled that enforcement would most likely be beyond the federal government's jurisdiction, given that marijuana used in the program is grown locally and noncommercially and does not cross state lines. The case is Ashcroft v. Raich, No. 03-1454.

In the second case, the states of New York and Michigan are defending their prohibitions against the shipment of wine from out-of-state wineries directly to consumers. New York's law was upheld and Michigan's struck down by separate federal appeals courts. The question in both Granholm v. Heald, No. 03-1116, the Michigan case, and Swedenburg v. Kelley, No. 03-1274, from New York, is whether the laws are supported by the states' 21st Amendment authority to regulate alcohol sales or whether, to the contrary, they impose unconstitutional barriers against interstate commerce.Free Speech

For the third time in recent years, the court will decide the constitutionality of a government-sponsored program of promoting an agricultural commodity through an assessment on producers. In this case, Veneman v. Livestock Marketing Association, No. 03-1164, it is the "Beef: It's What's For Dinner" advertising campaign, run by the Department of Agriculture and supported by an assessment of $1 for each head of cattle sold.

Dissident cattle producers won an appeals court ruling that the program amounted to government-compelled speech in violation of the First Amendment. Other federal courts have also recently struck down two other campaigns, "Got Milk?" and "Pork: The Other White Meat." As a result, the government's decades-old commodity promotion program is in turmoil.

Property Rights

In a case from New London, Conn., the court will examine the power of eminent domain and decide whether the government can take private property and turn it over to a private developer for a project intended to increase the local tax base. The question in Kelo v. City of New London, No. 04-108, is whether this is the kind of "public use" for which the Constitution authorizes eminent domain.

Discrimination

Cases concerning age, sex, race and disability discrimination are all on the docket. In a Mississippi case, Smith v. City of Jackson, No. 03-1160, the question is whether the federal law against age discrimination in employment requires proof of intentional discrimination, or whether a policy that has an unfavorable impact on older workers, regardless of intent, can be successfully challenged.

The sex discrimination case, Jackson v. Birmingham Board of Education, No. 02-1672, originating in Alabama, involves Title IX, the federal law that bars sex discrimination in educational programs, including athletics. The question is whether someone who suffers retaliation for bringing a Title IX complaint can obtain redress under the law.

Johnson v. California, No. 03-636, is a challenge by a black prison inmate to California's policy of segregating inmates by race for the first 60 days after arrival into the prison system or transfer within it. The question is whether courts should defer to prison officials' claim of necessity for an explicit racial classification that in any other setting would clearly be unconstitutional.

The disability case, Spector v. Norwegian Cruise Line Ltd., No. 03-1388, asks whether the Americans With Disabilities Act covers foreign-flag cruise ships. There may also be a gay rights case on the docket. On Friday, the American Civil Liberties Union asked the court to decide the constitutionality of a Florida law that categorically bars gay men and lesbians from adopting children.