Tune in to HLN's "Nancy Grace" at 9 p.m. ET Tuesday for more on Warren Jeffs' sentencing.
San Angelo, Texas (CNN) -- Polygamist leader Warren Jeffs was sentenced Tuesday to life in prison plus 20 years for sexually assaulting two girls he claimed were his "spiritual wives."
Jeffs, 55, will have to spend at least 45 years in prison before being eligible for release, according to Jerry Strickland, spokesman for the Texas Attorney General's office.
The jury sentenced Jeffs to life in prison for aggravated sexual assault of a 12-year-old girl and 20 years in prison for the sexual assault of a 15-year-old girl. He must serve at least 35 years of the life sentence and half of the other sentence, Strickland said. The judge in the case ordered that the sentences be served consecutively.
"Justice has been served," Jeffs' nephew, Brent Jeffs, told InSession soon after the sentence. He testified during the penalty phase of his uncle's trial that Jeffs raped him when he was 5 years old.
"I finally had this day and it was an awesome day in court to be here, involved in all of this," said Brent Jeffs, now 28.
Jeffs perverted his position as the head of the Fundamentalist Church of Jesus Christ of Latter-day Saints to "satisfy his own personal appetites and desires," prosecutor Eric Nichols said.
Those appetites included forcing sex on the two girls, 12 and 15, who he had taken as wives, prosecutors said.
Audiotapes seized from his car and the church's Yearning For Zion Ranch compound in Eldorado, Texas, and played for jurors during his trial, depicted Jeffs offering "celestial marriage" instructions to the young wives, according to prosecutors.
"You have to know how to be sexually excited and to help each other ... and you have to be ready for the time I need your comfort," a man's voice says. "This is your mission. This is how you abide the law.
At one point, the man says, "Take your clothes off. Do it right now," followed by the sounds of crying.
"Just don't think about the pain; you're going to heaven," the man says.
"Rarely if ever in the criminal justice system in Texas have we ever encouraged a person such as Warren Jeffs, whose criminal conduct spans decades, multiple jurisdictions and hundreds of victims," Nichols said.
A former member of the church, Rebecca Musser, said the verdict will not bring back lost innocence. But she said it can help others escape from abuse they may have suffered.
"Whether the currency is God or greed, the trafficking of women and children for sex is a form of slavery," she said.
Jeffs is the eighth person from the ranch to be convicted on sexual assault, bigamy and other charges, according to the Texas Attorney General's office. Four others are awaiting trial.
Attorney General Greg Abbott said he believes authorities have rooted out the molesters from the ranch, but will continue to monitor the church's activities there.
"We have an ongoing open investigation that will evaluate all evidence about any kind of wrongdoing out there at the compound whatsoever," Abbott said.
Jurors came back with the sentence after 30 minutes of deliberations Tuesday.
They began their work Tuesday morning following brief closing statements by prosecutor Nichols. Jeffs, who has argued that he and his faith were being persecuted, instructed his attorneys to deliver no closing statement.
"This is not the prosecution to persecute a people, this is a prosecution to protect a people," Nichols told jurors.
Jeffs did not attend the closing statement.
In addition to tape recordings that the state said depicted sex acts with minors, prosecutors also presented evidence that Jeffs knew he was wanted by federal authorities and that his behavior would be shunned by outsiders.
FBI Special Agent John Broadway testified that Jeffs ordered the destruction of various discs and transcripts three days after an arrest warrant was issued for him on June 10, 2005. The polygamist sect leader established "houses of hiding," allegedly with young girls for him to marry, Broadway said.
The FBI agent also read from a priesthood record, in which Jeffs allegedly wrote: "Things are happening so quickly. There is an even younger girl that the Lord wants me to take. She is 13. For some reason the Lord is sending me these girls that can be worked with."
Jeffs also wrote: "If the world knew what I was doing, they would hang me from the highest tree," according to evidence presented in court.
Referring to that comment, prosecutor Nichols said during his closing statement that "Yes, this is Texas. But no, we don't hang convicts anymore from the highest tree, and we don't have the ability to call down the wrath of the Almighty ... We as a people choose to isolate our worst offenders, to keep them away from their past and future victims."
Jeffs' breakaway sect is believed to have about 10,000 followers. Their practice of polygamy, which the mainstream Mormon Church renounced more than a century ago, is part of the sect's doctrine.
InSession's Jim Kyle contributed to this report.