The woman has 10 children, and Ruby Gutierrez, an investigator for the state department of Child Protective Services, testified Monday that two adult sons took underage brides and three daughters were given in marriage when they were underage.
The children's father allegedly blessed the girls' marriages.
Two of the girls are now older than 18.
The hearing ended after child welfare attorneys finished presenting their evidence Monday evening and was scheduled to resume Tuesday morning with witnesses for the mother.
During the proceedings, Texas Ranger Nick Hannah introduced into the record dozens of documents seized from the Yearning For Zion Ranch in Eldorado showing marriages recorded in certificates, photos and church census documents. He said the 30 documents introduced at the hearing were among "hundreds of thousands" of documents taken from the ranch in April.
The mother refused to answer about 50 questions asked by attorneys for the child welfare agency, including what constituted abuse, the names of her children and her relationship with their father.
"I stand on the Fifth (Amendment)," she said repeatedly in a flat tone.
Her attorney, Gonzalo Rios, said the woman was exercising her right against self-incrimination because of the continuing criminal investigation. Two of her husband's sons have been indicted on charges of sexual assault of a child, as has Jeffs.
In documents submitted with the state's custody petition, the 14-year-old girl is quoted as telling a caseworker that a young teenage girl marrying an older man "can't be a crime because Heavenly Father is the one that tells Warren when a girl is ready to get married."
Carolyn Jessop, now a best-selling author, testified about her relationship with the girl's father, from whom she ran away.
Carolyn, his fourth wife, said the man harshly disciplined her son, who was 1 at the time, by alternately spanking him and putting his face under a running faucet until it turned blue.
The father, who did not attend the hearing Monday, allegedly described the discipline as "breaking them" and used it on his children when they were young to teach them to fear authority.
She said the girl's mother once refused to take another son to the hospital when he broke his arm.
Under cross-examination, Rios sought to discredit Carolyn Jessop, saying most incidents she described occurred two decades ago. He also criticized her for the money she has earned from her book, "Escape," about her experience in the Fundamentalist Church of Jesus Christ of Latter Day Saints community.
Gutierrez, the child welfare investigator, said she didn't believe the couple's younger children could safely remain with their mother, citing the parents' previous failure to try to prevent sexual abuse because of their blessing of underage marriages. The state dropped its effort to also take custody of their 17-year-old son, saying he is old enough to protect himself.
But when asked about the danger to the 11-year-old boy, Gutierrez said, "If a 12-year-old has been married to a gentleman over the age of 50, there is no way a sibling doesn't know that and hasn't had to cope with that knowledge."
Child welfare authorities have been investigating the cases of 440 children since the Texas Supreme Court ordered that the children removed from the YFZ Ranch in April be returned to their parents. The state has asked the court to dismiss cases involving 76 children, including nine who have turned 18 since the custody case began; the remaining cases are still under investigation.
Monday's hearing was the first Child Protective Services effort since the court ruling to retake custody of FLDS children. The high court said the agency previously overreached in sweeping all the FLDS children into state custody, noting it showed no more than a handful of teenage girls were abused or were at risk of abuse.
Willie Jessop, an FLDS spokesman, said nothing has happened to justify the children being removed again. None of the seven children the state wants back in foster care currently live at the ranch.
"They couldn't find (abuse) the first time it came up. What's changed?" he said.
Willie Jessop also noted that the church made it clear it wouldn't sanction underage marriages and that doctrine has been in place for more than two years.
The FLDS believes polygamy brings glory in heaven. It is a breakaway sect of the mainstream Mormon church, the Church of Jesus Christ of Latter-day Saints, which renounced polygamy more than a century ago.
Jeffs, already convicted as accomplice to rape in Utah and awaiting trial on similar charges in Arizona, was indicted along with four followers in Texas last month on charges of sexual assault of a child. One of the followers was also indicted on a bigamy charge.
A sixth man, Dr. Lloyd Hammon Barlow, was indicted on three misdemeanor counts of failing to report child abuse. Authorities are seeking custody of his two daughters, saying he didn't report the babies he delivered to underage girls and that he married a 16-year-old.
