The Blackmores will be sentenced April 13. They face up to five years in prison.
The three defendants were members of the Fundamentalist Church of Jesus Christ of Latter-Day Saints, a polygamous offshoot church that has members in the community of Bountiful in southeastern British Columbia. The church's headquarters is in Hildale, Utah, and adjoining Colorado City, Ariz., and the trial was watched by current and former FLDS members in both countries.
It is thought to have been the first time polygamists in Canada were tried for allegedly facilitating children's underage marriage or the sex that followed.
The charges against the Blackmores centered on a 13-year-old girl who records show was married to FLDS President Warren Jeffs in 2004. Jeffs was 48 at the time. He is now serving a life sentence in Texas.
Oler was accused of bringing the 15-year-old girl across the border to marry James Leroy Johnson, who was 24 at the time of the marriage. That ceremony was on June 25, 2004, in Mesquite, Nev.
Much of the evidence heard in the judge-only trial arose from a U.S. investigation into Jeffs and the FLDS. But the Royal Canadian Mounted Police also traveled to Utah, Arizona, Texas and other U.S. states to build their case. Witnesses included U.S. law enforcement and former FLDS members.
Brandon Blackmore's lawyer John Gustafson told the judge in his closing submissions that the prosecution failed to prove his client transported the girl across the border or that he knew beforehand that sexual contact with an older man would result.
Gail Blackmore is also known as Emily Gail Crossfield.
Salt Lake Tribune reporter Nate Carlisle Contributed to this story.