ST. GEORGE, Utah — The leader of a polygamous Mormon splinter group was convicted today of being an accomplice to rape for performing a wedding between a 19-year-old man and a 14-year-old girl.

Warren Jeffs, 51, could get life in prison after a trial that threw a spotlight on a renegade community along the Arizona-Utah line where as many as 10,000 of Jeffs’s followers practice plural marriage and revere him as a mighty prophet with dominion over their salvation.

Jeffs stood and, like his 15 followers in the courtroom, wore a stoic look as the verdict was read.

“Everyone should now know that no one is above the law, religion is not an excuse for abuse, and every victim has a right to be heard,” the Utah attorney general, Mark Shurtleff, who had endorsed the prosecution in Washington County, said.

A defense attorney, Wally Bugden, who told jurors that Jeffs was a victim of religious persecution, declined to comment.

Prosecutors said Jeffs forced the girl into marriage and sex against her will.

The jury deliberated about 16 hours over three days. This morning, the judge replaced a juror with an alternate for undisclosed reasons.

While polygamy itself was not on trial — the couple were monogamous — the case focused attention on the practice of polygamy in Utah, where it has generally been tolerated in the half-century since a government raid in 1953 proved a public relations disaster, with children photographed being torn from their mothers’ arms.

Jeffs succeeded his father in 2002 as president of the Fundamentalist Church of Jesus Christ of Latter Day Saints, or FLDS. Former members say he rules with an iron fist, demanding perfect obedience from followers and exercising the right to arrange marriages as well as break them up and assign new spouses.

At the trial, widely different versions of the relationship — and Jeffs’ influence — were presented by the woman, now 21, and her former husband, Allen Steed, 26.

At their wedding in 2001 at a Nevada motel, the woman said, she cried in despair when pressed by Jeffs to say “I do” and had to be coaxed to kiss her new husband. The woman testified that FLDS girls receive no information about their bodies or reproduction. She said she didn’t even know sex was the means by which women had babies.

The woman said the couple were married for at least a month before they had intercourse, her husband telling her it was “time for you to be a wife and do your duty.”

“My entire body was shaking. I was so scared,” she testified. “He just laid me on the bed and had sex.”

Afterward, she slipped into the bathroom, where she downed two bottles of over-the-counter pain reliever and curled up on the floor, she said. “The only thing I wanted to do was die,” she said.

But Mr. Steed testified that his teenage bride initiated their first sexual encounter, approaching him after he fell asleep in his clothes after a 12-hour day at work.

Under Utah law, a 14-year-old can consent to sex in some circumstances. But sex is not considered consensual if a person under 18 is enticed by someone at least three years older.

For reasons prosecutors have never explained, Mr. Steed has not been charged with a crime.

The mainstream Mormon Church, or the Church of Jesus Christ of Latter-day Saints, renounced polygamy more than a century ago, excommunicates members who engage in the practice, and disavows any connection to the FLDS church.

Jeffs is also charged in Arizona with being an accomplice to both incest and sexual misconduct with a minor for arranging marriages between two underage girls and relatives of theirs. In addition, Jeffs is under federal indictment in Utah on charges of fleeing to avoid prosecution.

The charismatic Jeffs was captured in a traffic stop last year just outside Las Vegas after about 18 months on the run. At the time, he was on the FBI’s 10 Most Wanted list, alongside such figures as Osama bin Laden.

Jeffs was in a red Cadillac Escalade in which investigators found more than $57,000, cell phones, prepaid credit cards, wigs and sunglasses.

Since at least the 1920s, members of the FLDS have lived in the twin towns of Colorado City, Ariz., and Hildale, Utah, where the women wear long prairie dresses and have long braided hair, and the men dress modestly too, often in buttoned-up shirts.

All homes and other property were kept in a trust controlled by Jeffs and other church leaders until a judge in 2005 put an accountant in charge because of allegations of mismanagement.