After being duped by false leads and chastised by a court for its handling of polygamist sect children, the state of Texas has won a criminal conviction in its first trial of a sect member charged with sexually assaulted an underage girl.

Raymond Jessop, 38, was convicted late Thursday for having sex with the teen with whom he had a so-called spiritual marriage. He faces up to 20 years in prison when the jury reconvenes Monday to begin deciding his sentence.

Early on, the weeklong raid of the Yearning For Zion Ranch was hounded by missteps. After scouring the ranch for days in April 2008 in search of a caller who claimed to be an abused girl, law enforcement acknowledged "Sarah Barlow" didn't exist.

Several weeks after Texas child welfare officials put all 439 sect children in foster care in one of the largest child custody cases in U.S. history, an appellate court ruled that Texas authorities had overstepped, and the children went back to their parents.

But authorities still seized documents from homes and concrete vaults in the towering limestone temple and annex building at the ranch — documents that would help convict Jessop and indict 11 other members of the Fundamentalist Church of Jesus Christ of Latter Day Saints.

Jurors deliberated for little more than two hours before convicting Jessop, who did not visibly react as the verdict was read. Free on bond during trial, he was immediately handcuffed and led to jail.

Lawyers in the case declined to comment on the verdict Thursday.

Jessop allegedly has nine wives. He also faces a bigamy charge, but that case is to be tried later. The girl in the assault case, now 21, was previously in a spiritual marriage with Jessop's brother before being "reassigned" to Jessop when she was 15, according to documents seized at the ranch. She became pregnant at age 16.

Generally, under Texas law, no one under 17 can consent to sex with an adult.

"Any act of sexual assault is a horrendous crime, but an act of a sexual assault of a child is of such an extreme nature we don't even consider whether the victim was able — much less did — consent," Assistant Attorney General Eric Nichols said during closing arguments as he stood before photos of the young mother and toddler in prairie dresses.

"There is a sound foundation based not just in documents, based in DNA evidence for which the documents serve as corroboration ... that Raymond Merril Jessop behind those gates, behind that guard house, behind those walls, sexually assaulted" the then-teen, he said.

Forensic experts who testified during the trial, which began with the largest jury pool in the small county's history on Oct. 26, said there was a nearly 100 percent probability Jessop was the father of the woman's daughter, who is now 4.

Jessop's attorneys had argued that no witness placed Jessop in Schleicher County at the time of the alleged assault in November 2004. They said prosecutors instead relied on only small snippets of documents to place Jessop and the teen at the ranch at the time of the alleged assault.

The defense offered no witnesses at trial and provided no evidence Jessop was elsewhere.

Nichols used a photo album, family records and dictations by jailed sect leader Warren Jeffs to establish a time line that put Jessop and the teen at the ranch when she became pregnant. The records covered parts of 2004 and 2005, but not specifically the time of the alleged assault.

The woman was on the prosecution's witness list, but did not testify.

Twelve men from the sect have been indicted on charges ranging from failure to report child abuse to sexual assault since authorities raided the ranch.

Jeffs was convicted in Utah as an accomplice to rape and awaits trial in Arizona on charges related to underage marriages there. He'll then face separate sexual assault and bigamy charges in Texas.

The sect broke away from the mainstream Mormon church, which renounced polygamy more than a century ago.

The jury was told Jessop was legally married to another woman before entering the spiritual marriage, but only as proof that Jessop could not have been legally married to the teen.