SAN ANGELO -- Polygamist sect leader Warren Jeffs was convicted Thursday of sexually assaulting two child brides after a weeklong trial in which he insisted on representing himself, only to remain silent through most of the proceedings and present just one witness -- a church elder who gave an extended Sunday school lesson on its beliefs.Jeffs, 55, head of the Fundamentalist Church of Jesus Christ of Latter Day Saints, stood stone-faced as a verdict of guilty on two counts of sexual assault of underage girls was read after the jury of 10 women and two men deliberated for 31/2 hours.He had stood without speaking for all but a few seconds of the 30 minutes allotted for his closing argument. Once, he turned and looked toward prosecutors and the jury, most of whom avoided direct eye contact with him. "I am at peace," he mumbled, then said no more.Earlier, Jeffs asserted that his religious rights were being trampled and that God would seek revenge if the trial continued.The maximum sentence is life in prison. The sentencing phase of the trial began after the verdict was announced.Prosecutors introduced DNA evidence to show that Jeffs fathered a child with a 15-year-old girl and played an audio recording of what was said to be Jeffs sexually assaulting a 12-year-old. They also played recordings in which Jeffs was heard instructing young women on how to please him sexually -- and thus, he told them, please God.The FLDS, which has at least 10,000 members, is a radical offshoot of mainstream Mormonism and believes polygamy brings exaltation in heaven. Members consider Jeffs to be God's spokesman on earth.Police raided the group's remote West Texas Yearning for Zion ranch in April 2008, and more than 400 children who had been placed in protective custody were eventually returned to their families.'A good wife'As the sentencing phase began, prosecutors told jurors that they will present evidence that Jeffs had 78 wives in addition to his legal spouse and that 24 were under 17. Prosecutor Eric Nichols also said he will show that Jeffs witnessed or performed more than 500 polygamist marriages as well as 67 other church marriages involving underage girls.Jeffs stood and made several incoherent objections to what Nichols said -- something he did frequently throughout the trial."I object to anything pertaining to a religious manner," he said. "A constitutional guarantee involving things sacred must be invoked."Prosecutors relied heavily on information seized from the compound 45 miles south of San Angelo. It features a massive, four-story temple of white limestone. Much of the material was discovered in a vault at the end of a secret passageway in the temple and another vault in an annex building.On one of the recordings played at the trial, Jeffs referred to "drawing close" or "being close," which authorities testified is how church members refer to sex. Two female voices were recorded saying, "OK.""A good wife is trained for her husband and follows the spirit of peace," Jeffs said on the recording.Another audio recording included Jeffs and the 12-year-old girl and was made in August 2006 at the Texas compound. Played in court, it was difficult to decipher, but Jeffs' and a female voice are heard. He says, "I perform this service in the name of Jesus Christ, Amen," then says the girl's name. When she says something, he responds, "Don't talk while praying." Several minutes of heavy breathing followed.Jeffs read a statement, which he claimed was from God, promising a scourge of biblical proportions against all involved if the case against him didn't cease, and three times he tried to have the judge removed.In the meantime, he refused to cross-examine the state's witnesses.The lone defense witness Jeffs called, church elder J.D. Roundy, spent 41/2 hours reading from Mormon scripture and talking about his faith as a member of the FLDS but said nothing about the defendant himself or the crimes he was accused of.Prosecutors said the case had nothing to do with Jeffs' church or his beliefs.