The Federal Trade Commission is investigating whether lawyers who represent indigent defendants in D.C. Superior Court would violate free-trade laws if they carry out their threat to go on strike Sept. 6 in a dispute over pay.

Officers of the Superior Court Trial Lawyers Association said they were notified by an FTC investigator yesterday that the investigation is under way. Ralph J. Perrotta, president of the organization, said he was given few details of what the investigation entails, but was told it concerns how collective actions that the lawyers might take could affect prices at the court.

Attorney Jacob A. Stein, former D.C. Bar president who is representing the association, said he also was notified of the investigation in a telephone conversation with an FTC attorney.

Kenneth Starling, director of the FTC's Bureau of Competition, yesterday declined to either confirm or deny that the lawyers' proposed strike is being investigated.

"It sounds like a labor union being prosecuted for negotiating a wage," said one attorney familiar with the talks. "I've never heard of an investigation like this."

Sources said the current FTC investigation is similar to another action brought four years ago against doctors in Michigan who had threatened to boycott their patients unless state cuts in Medicaid reimbursements were restored.

State officials restored about $4 million in physicians' fees after the Michigan State Medical Society presented numerous post cards signed by doctors saying they would cut off treatment to Medicaid patients if the state carried out its plan.

In March the FTC ruled that the boycott threat was illegal. The doctors, the commission ruled, "had undertaken conspiratorial and coercive activity with respect to prices."

A court strike could run into similar problems, sources said, because the lawyers are not union members and technically compete with each other for clients.

The FTC action comes on the eve of talks between the lawyers and D.C. Mayor Marion Barry, who are scheduled to discuss the dispute Monday.

"I'm disappointed that the only signal we've gotten since announcing the strike is that the powers that be intend to confront us head on," Perrotta said. "There's been no inkling up to now of an accommodation."

The lawyers, who are paid by the city to represent most of the indigent defendants who come before the court, have not received a pay raise in 12 years. Spurred by Senate approval in July of about $25 million in additional funds for the city's corrections system and the court, the lawyers voted Aug. 11 to strike unless they get a pay boost.

They are now paid $30 an hour for court appearances and $20 an hour for work done out of court under a voucher system supervised by the court, which appoints the attorneys to represent specific defendants.

D.C. Bar officials, who testified before the City Council earlier this year in support of a raise for the attorneys, say those rates are far less than what most firms pay their most junior associate lawyers.

This week, members of the trial lawyers association reaffirmed their strike vote and agreed to push for an hourly rate of $55 for court appearances. They also agreed to picket the court beginning at 1 p.m. Sept. 6 and to refuse to accept any new cases, even if threatened with contempt citations.

The city would be required by law to supply lawyers for indigent defendants regardless of the strike. To prevent other lawyers from crossing the picket lines, strike organizers began mailing literature yesterday detailing their complaints to about 40 law firms and other attorneys identified as possible court replacements.

Legislation before the City Council Judiciary Committee would raise the pay rate to $35 for work in or out of court. That would cost about $2.5 million next year, and city officials say there is no money in the budget for the increase.