Patricia Matassarin, Jessop's attorney, questioned how a person proves her age if officials won't believe a birth certificate or driver's license, which Jessop also gave the state.

"The issue is, how does anyone prove the date of their birth? We don't get a date stamp when we're born," Matassarin said.

A birth certificate combined with testimony from Jessop's mother were presented, and state officials conceded in Austin on Thursday that Jessop is an adult.

Crimmins said many of the sect members whose ages are in dispute don't have documents typically used to establish age, like birth certificates, drivers' licenses or public school records. FLDS children were home-schooled.

"We've been trying, sometimes with very little success, to get as much information as possible on the children," he said. "What we've said is consistent. We think there was some abuse — some physical abuse and some sexual abuse — at the ranch. This ranch was considered as a very large household."

The children are being treated the same as siblings of abused children in smaller households, where removal is common, Crimmins said.

The FLDS case is one of the most complicated custody cases in U.S. history, but all the children from the ranch were sent to foster care after state District Judge Barbara Walther found they were being abused or were at risk for abuse because adults were pushing underage girls into sex and marriage with older men.

In Texas, girls who are younger than 17 generally cannot consent to sex with adult men. No one has been arrested or charged in the case.