Prosecutors trying polygamist leader Warren Jeffs on child sexual assault charges plan to use the DNA of a child conceived in a union with a 14-year-old girl to convict him in a Texas court.

Jeffs, the leader of a breakaway Mormon sect, is charged with child sexual assault and aggravated child sexual assault in connection with his "spiritual marriages" to two girls, ages 12 and 14, at the remote Yearning for Zion Ranch in Texas.

"You will hear and see evidence that as a result of sexual activity a child was conceived, and from the DNA evidence you will be able to determine that Warren Steed Jeffs is the father of this child," Assistant Texas Attorney General Eric Nichols told the jury at the start of the trial.

Prosecutors said they would also present an audio tape of a sexual encounter between Jeffs, 55, and the 14-year-old that he secretly recorded.

Jeffs is considered the spiritual leader of the Fundamentalist Church of Jesus Christ of Latter Day Saints, which has been condemned by the mainstream Mormon Church and is accused of promoting marriages between older men and girls.

The sect, which experts estimate has 10,000 followers in North America, also teaches that for a man to be among the select in heaven, he must have at least three wives.

Nichols also called a string of law enforcement witnesses who testified about a 2008 raid on the Texas ranch in which the two girls and more than 400 other children were taken into protective custody, and about Jeffs' 2007 arrest in Nevada.

Jeffs sat silently, alone at the defense table, with his head bowed and his hands folded in his lap, in what appeared to be a position of prayer. He never spoke to question witnesses or to object to testimony.

Danny Guajardo, a Texas Attorney General's Office investigator who took DNA samples from the two girls and the baby, was expected to discuss his findings on Friday.

WILL REPRESENT HIMSELF

Jeffs had thrown the trial into disarray earlier on Thursday when he fired his defense lawyers and demanded the right to represent himself, which the judge then granted.

"It's not as easy as it looks on TV, Mr. Jeffs," State District Judge Barbara Walther told him. "You're on your own."

Jeffs, who founded the ranch in 2003 as an outpost for his church after decades on the Utah-Arizona border, refused to enter a plea, so the court recorded a "not guilty" plea.

"My counsel doesn't have the full understanding of the facts and are unable to assist in my defense," Jeffs told the court in a slow, halting voice as he explained his move to fire his counsel.

"I have trained my defense, but they were unable to do what I said. I am presenting the need for true justice to be presented, and for the truth to come out."

Jeffs has fired myriad attorneys in what prosecutors said was an attempt to delay the trial on charges that could send him to prison for life. Judge Walther instructed his attorneys to remain on standby although they do not have to appear in court as his advisers.

There were no signs of any sect members or supporters of Jeffs in the half-full courtroom.

Before being fired, defense attorneys had worked to exclude evidence seized when Jeffs was arrested in Nevada in 2007, as well as items seized from the ranch in 2008.

Defense lawyers said those items shouldn't be used. They include a list of adult male members of the sect detailing their numerous wives and a photograph of a grinning Jeffs kissing one of his brides.

They argued against that evidence because the raid was prompted by a false report to a San Angelo domestic violence hotline by a woman falsely claiming to be a 16-year-old child bride. The raid resulted in hundreds of children being temporarily removed from the compound.

Court Arizona Attorney general Arizona