WASHINGTON - The Supreme Court, urged by a group of states to remove a constitutional obstacle to prosecuting fraud by professional fund-raisers, agreed yesterday to clarify the boundary that separates charitable solicitation from consumer fraud.

The case was brought to the court by the Illinois attorney general's office, which for 10 years has tried to pursue a consumer fraud action against a telemarketing company that keeps 85 percent of the money it raises on behalf of a Vietnam War veterans' charity.

The state's complaint against Telemarketing Associates Inc. was dismissed last year by the Illinois Supreme Court on the ground that charitable solicitation is a form of speech that is protected by the First Amendment.

A trio of decisions by the Supreme Court in the 1980s established that principle and held that state regulators were constitutionally barred from designating a particular percentage of receipts that had to reach a charity for the fund raising to be considered legitimate.

In the appeal yesterday, which was backed by a brief from 18 other states, Illinois is arguing that the state court misinterpreted those precedents in a manner that "transformed the First Amendment into a license for unscrupulous fund-raisers to defraud the public in the name of raising money for charity."

The state said the question for the justices was "whether a professional fund-raiser has a First Amendment right to mislead people into giving money by representing that it will be used for charitable purposes, when actually the fund-raiser keeps the vast majority of all money donated."

While high fund-raising costs alone could not establish fraud, the state said, neither should the costs be deemed irrelevant.

The telemarketing firm's contract called for it to retain 85 percent of the money it raised on behalf of VietNow, an Illinois-based charity with the mission of providing food, shelter and financial support for needy Vietnam War veterans. The telemarketer revealed this arrangement in the disclosure form it filed with the state but did not pass the information on to potential donors.

Urging the Supreme Court not to take the case, Telemarketing Associates said it spent a portion of its fee on various educational projects on behalf of VietNow, making the 85 percent figure alone an unreliable indicator of the benefit the charity received from the relationship.

Among other developments yesterday, the court agreed to examine the standards for medicating mentally ill criminal defendants against their will in order to make them competent to stand trial. The court ruled 10 years ago that such defendants were entitled to a hearing before being forced to accept anti-psychotic medication, but that decision, Riggins v. Nevada, did not specify how the decision was to be reached.

The latest case is an appeal by a dentist from St. Louis who was charged by the federal government in 1997 with submitting false invoices to Medicaid. After being released on bond, he was charged the next year with conspiring to murder a witness and an FBI agent.

There is no dispute that the dentist, Dr. Charles T. Sell, is mentally ill and, in an unmedicated state, incompetent to stand trial.

A panel of the 8th U.S. Circuit Court of Appeals, in St. Louis, ruled 2-1 last March that the government could not achieve its important goal of bringing Sell to trial by any other, less intrusive means. The full 8th Circuit split 5-4 in declining last May to rehear the case.

The federal defender's office in St. Louis, representing Sell, asserts that the government "wants to medicate Dr. Sell into an artificially induced, drug-dependent competence." But "a citizen does not lose a fundamental constitutional right simply based on the fact that he is charged with a crime," the brief continues.