The U.S. Supreme Court will decide whether two million Comcast Corp. cable-TV customers in the Philadelphia area should be considered a damaged class in a lawsuit that seeks $875 million from the cable giant and has been wending its tortuous way through the federal courts for almost a decade.

The antitrust suit, filed in 2003, claims that Comcast clustered cable systems in Philadelphia through a series of swaps with other cable companies in the late 1990s, enabling it to control the market and raise cable prices.

The Supreme Court's announcement Monday that it would take the case is a victory for Comcast — the suit was scheduled for trial in September in Philadelphia. A high-court finding that the class certification does not meet legal standards would be blow for the plaintiffs and would send the case back for further litigation.

In a statement on its website regarding the case, Comcast v. Behrend, the Supreme Court said it would narrowly consider this issue: "Whether a district court may certify a class action without resolving whether the plaintiff class has introduced admissible evidence, including expert testimony, to show that the case is susceptible to awarding damages on a class-wide basis."

The justices' action will be watched closely and could set more stringent standards in class-action lawsuits.

"We are really expecting this to be the big one," said Ankur Kapoor, a partner and antitrust specialist with the New York law firm Constantine Cannon. "Whatever the Supreme Court says about this, the legal journals will be writing about it for years."

Eric Cramer, a managing shareholder in the Center City law firm Berger & Montague, who specializes in complex antitrust litigation, said a ruling "could raise the bar on what plaintiffs are required to prove at the class-certification stage" of litigation.

"This case is part of a recent trend at the Supreme Court," said Steven G. Bradbury, a partner in Dechert L.L.P.'s Washington office, who specializes in antitrust and appellate cases. The nation's highest court, he said, has emphasized that trial courts must conduct a rigorous analysis before allowing a case to go forward as a class action, even if that analysis overlaps with the issues a jury would have to decide at trial.

"The issue here," Bradbury explained, "is whether the plaintiffs have to show at the class-certification stage that they have a method of proving damages that is admissible at trial and common for all plaintiffs."

Both U.S. District Judge John R. Padova in Philadelphia and the U.S. Court of Appeals for the Third Circuit, also in Philadelphia, have ruled favorably on the class certification.

Comcast had no comment Monday on the pending litigation. This will be the company's first case before the Supreme Court.

Lead counsel for the plaintiffs in the case, Barry Barnett of the Dallas, Texas, law firm Susman Godfrey L.L.P., did not respond Monday to a phone call or e-mail. One of the named plaintiffs, Stanford Glaberson, was reached by phone, but declined to comment.

The lawsuit claims that Comcast made it difficult for RCN Telecom Services to expand and compete in Comcast's franchise areas in the Philadelphia region. Comcast fought RCN by targeting its potential customers with special deals and by using exclusive contracts to tie up technicians who might help with RCN's expansion, according to federal court documents. RCN could not break into the Philadelphia-area market, and the company later filed for bankruptcy protection.

Comcast v. Behrend has been relentlessly litigated for years, and the stakes are high for the media company. Similar cases have been filed against it in Chicago and Boston.