Angel Goodwin's comments came Tuesday in opening statements in the trial of Fredrick Merril Jessop, a former bishop in the Fundamentalist Church of Jesus Christ of Latter Day Saints, the San Angelo (Texas) Standard-Times reported.
"The state will prove beyond a reasonable doubt, that on July 27, 2006, Fredrick Merril Jessop married a freckled, 12-year-old girl to a 50-year-old man," Goodwin told jurors.
Jessop, 75, is charged with performing a ceremony prohibited by law. The third-degree felony carries a penalty of up to 10 years in prison and a $10,000 fine.
Jessop is accused of conducting a 2006 ceremony in which he married an underage girl to Warren Jeffs, the former sect leader sentenced to life in prison in August for sexually assaulting two girls, ages 12 and 15, who he took as polygamist wives.
Jessop had been a bishop in the sect before being excommunicated by Jeffs.
Two Texas Rangers testified Tuesday morning about the steps taken for getting trailer loads of documents and other evidence from the sect's west Texas Yearning for Zion Ranch in an April 2008 raid.