If the usual process occurs, the justices of the Supreme Court will gather around a large rectangular table Friday morning and, one by one, cast their votes on the constitutionality of President Obama’s health-care law.

They will let the rest of us know the outcome in due time.

It can take years for a controversy to reach the court and months for the justices to write the opinions that lay out the legal frameworks for their decisions. But they move with surprising speed to vote on cases they have heard, almost always within days of oral arguments. Then — silence.

In a town where secrets are hard to keep, the Supreme Court is a striking outlier. The justices and their clerks know the outcome of cases almost immediately, but it’s rare for rulings to become known before the justices announce them.

“It’s only a small number of people who know, and they just don’t leak,” said Orin Kerr, a law professor at George Washington University and a former clerk to Justice Anthony M. Kennedy. “I mean, you’re sworn to secrecy.”

The justices give no notice about when a decision is to be announced. It would seem most likely that their ruling on the sprawling trio of cases concerning the Patient Protection and Affordable Care Act will be one of the last announced this term, in the last week of June.

That can be a long wait, especially after this week’s historic three-day hearing that featured live updates from the court’s marble plaza and round-the-clock coverage from newspaper Web sites and blogs. Jeffrey Fisher, a former clerk and co-director of the Supreme Court Litigation Clinic at Stanford Law School, said the delay will be something of a lesson for the country.

“The Supreme Court is probably the closest thing we have in the country to a true deliberative body,” he said, meaning that the justices take their time and are required to sign their names to long expositions of the legal reasoning behind their decisions.

It will be interesting to see how the court’s final decision matches the tone of the oral arguments, which split largely along the court’s ideological divide. The questions at oral arguments are usually pretty true indicators of the justices’ leanings. But there are cases — especially those involving major constitutional issues — in which the tone can be misleading.

The process Friday will begin in the court’s conference room just off the chambers of Chief Justice John G. Roberts Jr. He will take his place at the head of the table, and his eight colleagues will arrange themselves by seniority. No one else will be in the room.

The court’s recent tradition has been that the chief justice lays out the case and then informs the others how he will vote. The process moves from justice to justice by seniority, and the rule is that no one speaks twice until everyone has spoken once.

Junior justices — on this court, Elena Kagan — are often surprised to find themselves casting the deciding vote. (It is also the junior justice’s job to take notes and answer the door if there is a knock.)

Despite their combative tone at oral arguments and cutting remarks in the final opinions, the justices invariably describe the conference room as a place of decorum and politeness.

“In that room, when we discuss First Amendment, abortion, Second Amendment, death penalty, preemption, commerce clause, the cases of great consequence — Bush v. Gore — I still have yet to hear the first unkind word,” Justice Clarence Thomas said in a speech last year.

If Roberts is in the majority after the vote, he will either decide to write the court’s ruling or choose the justice who will. If he is not, the senior justice on the prevailing side will make the assignment. A similar process will be underway among the dissenters, because every justice in every opinion puts his or her name on an explanation. Sometimes the justices write only for themselves.

Instead of the personal arm-twisting and individual conversations that might characterize Congress, justices say their negotiations come through reading draft opinions and informing the author of additions and deletions that might be needed to win unqualified support.

“There are a fair number of cases in which some justices disagree with the majority at the conference after oral argument but ultimately are persuaded to join its opinion,” retired justice John Paul Stevens wrote in his recent book “Five Chiefs.”

Illustrating the court’s sometimes antique ways, he wrote that the usual way to signal support is to tell the author to “please join me.” The better translation is “me join please.” It is a reference to the court’s style of saying that an opinion was written by a certain justice and “joined” by others.

The justices can change their votes after the initial conference, and most of the time they switch from the minority to the majority after reading the opinion.

“What’s more unusual is for a vote to change in a way to change the outcome,” said Fisher, who clerked for Stevens.

No one can say how often that happens. But the case that comes up in discussing the issue is the abortion-rights case Planned Parenthood of Southeastern Pennsylvania v. Casey . Kennedy was with conservatives in the early vote, which would have overturned Roe v. Wade. Instead, he joined an opinion that reaffirmed most of it.