Those priesthood records and other documents from the sect will be used by Canadian authorities to prosecute Blackmore and Crossfield Blackmore in a trial that is to start Tuesday in Cranbrook, British Columbia.
They and another Canadian who will be tried with them, former FLDS bishop James Oler, each are charged with one count of removing a child from Canada for the purposes of sex or sexual exploitation. They face up to five years in prison if convicted.
It's thought to be the first time polygamists in Canada have been put on trial for allegedly facilitating a daughter's underage marriage or the sex that followed.
"What I'm very sorry about is only these people are charged because there were so many others involved in shipping [additional] kids down" to be married, said Nancy Mereska, an Alberta resident and founder of the Stop Polygamy in Canada Society.
The trial figures to be the polygamy version of "Where in the World is Carmen Sandiego?"
Jurors will hear how FLDS members live in a region that stretches from Texas to Utah to 1,000 miles and one international border north in Lister, British Columbia.
FLDS members have resided there since the 1940s in a community they call Bountiful. It's just north of the Idaho Panhandle.
The jury also will hear about how law enforcement apprehended Jeffs as he was driving near Las Vegas in 2006 and about the 2008 raid on the Yearning For Zion Ranch in Eldorado, Texas. Much of the evidence against the Blackmores and Oler comes from records seized from Jeffs' Cadillac Escalade and from the ranch.
Those records recount Jeffs' marriage to Millie. They also recount how, on June 25, 2004, Oler's 15-year-old daughter, Carma Elaine Oler, was married in Mesquite, Nev.
According to those records, which have since been entered into court cases in British Columbia, Oler married a 15-year-old girl that day, too. Neither he nor the son-in-law he received that day, James Leroy Johnson, have been charged with any crimes in the United States.
The Royal Canadian Mounted Police also are believed to have a recording of Jeffs having sex with Millie. Brandon S. Blackmore, a half brother to Millie and the son of the defendant with the similar name, confirmed to The Salt Lake Tribune on Sunday that he will testify. He will authenticate Millie's voice on the recording, and corroborate the account of some church records, he said.
One person who won't be at trial is Millie. Brandon S. Blackmore said she remains loyal to Jeffs and the church and is unwilling to testify.
"She is really brainwashed," Brandon S. Blackmore said.
A lawyer representing the elder Brandon Blackmore did not return calls seeking comment. The British Columbia Ministry of Justice, through a spokesman, declined to comment. Investigators for the Royal Canadian Mounted Police did not respond to messages seeking comment.
Gail Blackmore as people in Canada's FLDS community know her and Oler have elected to represent themselves at trial, according to the Vancouver Sun, though the judge has appointed what's called an amicus to offer counterpoints to the prosecution's legal arguments.
The trial that begins Tuesday also may be a test of whether Canada can successfully prosecute polygamists. There is another trial scheduled for April 10 for Oler and the country's best-known polygamist, Winston Blackmore, who as of July had 27 wives and 145 children.
Oler and Winston Blackmore are charged with polygamy in that case, where prosecutors will again use documents obtained by American authorities.
But Tuesday's focus will be on the underage marriages. Mereska said she has used FLDS church records to document 53 Canadian FLDS girls who were married as teenagers between 1990 and 2006.
Twenty-four of those wedding ceremonies occurred in Utah, according to Mereka's list, with the rest occurring in other U.S. states or at the FLDS community in Lister.
Some of the brides married young men who were only a few years older, she said. Others married much older men, including another of Brandon Blackmore's teen daughters who married a 67-year-old.
If the defendants are convicted and the proceedings move to a sentencing hearing, Mereska plans to ask the judge to let her submit a statement on behalf of the victims, even though she has never met them.
"They would never come forward," Mereska said. "Never."