A polygamist sect leader defending himself against sexual assault charges broke his silence Friday with a 55-minute sermon defending plural marriages as divine and later said God would visit "sickness and death" on those involved if his trial wasn't immediately stopped.

Warren Jeffs, 55, could face life in prison if he's convicted of sexually assaulting two underage girls. He has been representing himself since he fired his high-powered lawyers Thursday, but he made no opening statement and spent hours sitting alone at the defense table staring into space in silence while prosecutors made their case.

On Friday, however, the ecclesiastical head of the Fundamentalist Church of Jesus Christ of Latter Day Saints suddenly cried "I object!" as FBI agent John Broadway testified about seizing eight desktop computers and 120 boxes and large folders of documents from the church's remote compound in West Texas in 2008.

"There is sacred trust given to religious leadership not to be touched by government agencies," said Jeffs, who leads an offshoot of mainstream Mormonism that believes polygamy brings exaltation in heaven. The sect's 10,000 members see Jeffs as a prophet who speaks for God on Earth.

Jeffs then launched into a lengthy defense of polygamy, but Walther eventually overruled his objection. She said court rules prohibited him from testifying while objecting but she let him go on at length because he hadn't offered an opening statement.

Jeffs then said he had no choice but to read a statement from God. Walther dismissed the jury and allowed him to read it.

"I, the Lord God of heaven," Jeffs read, "call upon the court to cease this open prosecution against my pure, holy way."

If the trial continues, the statement said, "I will send a scourge upon the counties of prosecutorial zeal to make humbled by sickness and death."

Jeffs has frequently said the charges against him are the work of over-zealous prosecutors.

Walther responded to the statement by telling Jeffs he could not threaten the jury.

"If you call for their destruction," she said, "or in any way say that they will be injured or damaged because of their service, you will be removed from the courtroom."

During afternoon testimony from Broadway and other witnesses who detailed documents seized from the FLDS compound, Jeffs objected so much that Walther eventually had a bailiff remove his microphones.

It was a sharp contrast to his earlier silence and halting speech. When answering questions from Walther earlier in the week, Jeffs usually paused for a full minute or two and then spoke in slow, deliberate tones interrupted by long, awkward pauses. But his words flowed freely Friday.

Jeffs, who is schedule for trial on bigamy charges in October, said his church has practiced polygamy for five generations and believes it is the will of God, who is a higher power than courts, state legislatures and the U.S. Congress.

"We are not a fly-by-night religious society . . . We are a community of faith and principles and those principles are so sacred. They belong to God, not to man and the governments of man," Jeffs said. He also noted that polygamy "is not of a sudden happening, it is of a tradition in our lives. And how can we just throw it away and say `God has not spoken?'"

Jeffs said FLDS members believe adhering to God's will, as stated by prophets like himself, is the only way to achieve eternal life in "Zion," or heaven.

"We do not seek your salvation," Jeffs told Walther and jurors, who watched and listened intently but made no visible reaction to his words. The judge turned down his repeated pleas for a separate hearing on freedom of religion.

Jeffs said Texas authorities had unfairly persecuted the FLDS just because its members are different from those of mainstream religions. Women in the sect wear prairie-style dresses and keep their hair tied up in tight buns that conjure images of frontier times.

"We are derided for how we dress, how we go about our laborers in a common society," he said. "The government of the United States had no right to infringe on the religious freedom of a peaceful people."

Jeffs said the courts and society are "not understanding our religious faith, yet judging it."

At the end of his speech, lead prosecutor Eric Nichols rose and said the Supreme Court ruled in the 1890s that religious freedom does not extend to polygamy.

The FLDS made headlines nationwide in 2008, when authorities raided its compound in tiny Eldorado, about 45 miles from San Angelo, after hearing allegations that young girls were being forced into polygamist marriages. More than 400 children were seized temporarily but eventually returned to their families.

Still, Jeffs and 11 other FLDS men were charged with crimes including sexual assault and bigamy.

All seven sect members prosecuted so far have been convicted and given prison terms of between six and 75 years.