After years of tumult in which many of its leaders have been jailed for obstruction of justice and charged in large damage suits, the Church of Scientology, with the support of mainstream religious groups, has begun to score a string of legal victories advancing its cause.

What has been derided as a cult offering patent-medicine psychology at sky-high prices now is being defended by some leading Christians and Jews as a persecuted minority. A $39 million fraud judgment has been overturned in a seven-year-old case that started the church's legal troubles, and a federal judge has extended the protections of the U.S. Trade Secrets Act to confidential church teachings.

At least 15 lawsuits filed around the country by former members still plague the 31-year-old U.S.-born church. Summonses are still out for the reclusive science-fiction author L. Ron Hubbard, 74, whose self-help writings form the church's doctrine but who has not been seen in public since 1980. Some of the church's tax exemptions have been revoked, and what it calls distorted versions of its most sacred texts have been released.

But with support from mainstream religious groups that have also rallied around the Rev. Sun Myung Moon, Scientology has begun to score court victories based on rules of court procedure and constitutional protections of freedom of religion. The judgments mean Scientology "will be tested in the great marketplace of ideas, and not in the courtroom," said trial counsel Earle C. Cooley, 53, a prominent Boston attorney who joined the church.

"We have experienced growth in the last six months that is unprecedented in our history," said the Rev. Ken Hoden, 38, president of the Church of Scientology of Los Angeles.

The church says it has 3.1 million members in this country and more than 6 million in the world. Hoden said the church has files proving these numbers, but outside experts are skeptical. "I've been unable to verify the figures," said J. Gordon Melton, director of the Institute for the Study of American Religions in Santa Barbara, Calif. "Certainly there are nowhere near that many people who are active Scientologists at present."

Hoden wears a clerical collar, and the church conducts Sunday services, weddings and funerals. But Hoden said his is a nondenominational religion that allows members to attend other churches.

The key turning point for the church came on July 16, when a circuit judge declared a mistrial in a Portland, Ore., case after a jury recommended a $39 million fraud judgment against the church.

The plaintiff in the suit, former Scientologist Julie Christofferson Titchbourne, 27, said the church had persuaded her to spend more than $3,000 on Scientology courses when she was 17. She said she was told she could improve her intelligence, eyesight and creativity. But she said she changed her mind after being put through an intensive course in anti-Scientology material by a professional "deprogrammer."

The jury recommendation in May led to daily demonstrations in front of the courthouse by thousands of Scientologists from around the world, including actor John Travolta, jazz musician Chick Corea and singer Al Jarreau.

When Multnomah County Judge Donald Londer ruled the case would have to be retried because Titchbourne's attorney had made improper and prejudicial arguments about the church, the demonstrators celebrated into the night and the church produced a videotape, "The Battle of Portland."

This month, U.S. District Judge Mariana R. Pfaelzer gave the church further control over confidential teachings being used by some of its critics. Pfaelzer ruled that church teachings constitute trade secrets protected by federal law, giving Scientology a legal victory potentially even more far-reaching than the Portland case. She said that religious secrets are the same as a private company's trade secrets, just as a secret chemical formula would be the property of a chemical company.

Even attorneys representing church critics acknowledge that Scientology has attracted many young Americans with a philosophy that emphasizes ethical behavior.

"Like most cult groups, they feed on idealism," said Boston attorney Michael Tabb, one of several lawyers handling anti-Scientology cases. "They're lonely, they're looking for something to give their life meaning," but church leaders "ultimately exploit them for the benefits of themselves."

Spokesmen for the mainstream religious groups that have supported the church, such as the National Council of Churches and the Coalition for Religious Freedom, emphasize they are not endorsing Scientological beliefs or methods, only their right to compete for converts without interference from the courts. Some defenders, such as National Council of Churches' Dean Kelley, also argue that "some of the church's offenses are not nearly as bad as the government has made them out to be."

In 1979 and 1980, eleven Scientologists, including Hubbard's third wife Mary Sue, were convicted of obstruction of justice in the burglarizing, bugging and planting of agents in government offices. Kelley said he thought the charge of burglary was too harsh, since the Scientologists had only photocopied documents inside the offices. Scientology minister Hoden said all the convicted members have been removed from policy-making positions.

L. Ron Hubbard is said to be writing science fiction at some undisclosed location in the United States. Courts have turned down efforts to have him declared dead.

Melton, the Santa Barbara-based expert who has followed church developments for years, agrees that there have been changes. "Ever since Church of Scientology International president Heber Jentzsch took over, he has been trying to undo some of the activities of his predecessors, especially in the guardians office."

That special branch of the church was set up as an intelligence-gathering arm to counter what Melton said was a U.S. government effort to discredit Scientology abroad.

Melton said he thought the church would eventually recover from the blow to its reputation, "but it will take at least a decade to get out from under that."

Tabb said the church still harasses former members and their supporters. He charged the church spent at least $25,000 to fabricate a check-forgery accusation against Boston attorney Michael Flynn, one of the church's leading critics. Hoden said the charge against Flynn is being investigated by a Boston grand jury.

The church has also been denied the right to let members deduct the money they spend for church services called "auditing," a form of counseling using a device designed to measure small amounts of electric current in the skin. The church says auditing helps members uncover disabling personal habits. It says the money paid by the individual being audited is a donation, but the courts, while still recognizing the church as a tax-exempt body, have disallowed these deductions.

Attorneys representing church defectors say Scientology's recent legal victories are temporary. In the Oregon case, "our feeling was that we made the mistake of asking for too much money," one attorney said. The Oregon case is expected to be tried again.

The recent victories in Los Angeles have also been tainted by publication in The Los Angeles Times of a summary of secret church documents held under seal in Superior Court. When the ban on public viewing of the documents was lifted briefly, 1,500 Scientologists crammed three floors of the courthouse to block public access.

The Times, however, said its reporters obtained the documents from the court file. It said the documents trace destructive human behavior back to a tyrannical ruler named Xemu who, to cure overpopulation on Earth 75 million years ago, herded people and extraterrestial beings into volcanoes and dropped H-bombs on them. Their spirits, called thetans, carried the seeds of aberrant behavior and still attach themselves to humans today, although Scientology says it can help eradicate them.

Hoden called the Times version of the documents "purposely distorted" and said they were designed only "to hold the church up to ridicule and contempt." He said church doctrine forbade any Scientologist from commenting on sacred writings.

Cooley, the church's principal litigator, likened Scientology to the early days of the Church of Jesus Christ of Latter-Day Saints. This too was a young American-born religion persecuted for diverging from mainstream doctrine, but drawing members through its commitment to strict moral values, he said.

He said he was not a member when he was first retained to defend the church. He said he joined because, in studying the church as part of his legal preparations, "I found it to be exactly what they had said it was, an applied religious philosophy that works in day-to-day life."