CRANBROOK, B.C. -- A former couple from the polygamous community of Bountiful, B.C., have been found guilty of taking a 13-year-old girl into the United States to marry the now imprisoned leader of the sect that practises plural marriage.

Justice Paul Pearlman of B.C. Supreme Court found former husband and wife Brandon Blackmore and Gail Blackmore guilty of the charge of taking a girl across the border for a sexual purpose in 2004.

He found James Oler not guilty of the same charge, saying he couldn't prove that the man crossed the border in 2004 with a 15-year-old girl who was later married to a member of the polygamous church.

The Blackmores will be sentenced April 13.

The court in Cranbrook, B.C., heard during their trial late last year about the polygamous beliefs and practices in the Fundamentalist Church of Jesus Christ of Latter-Day Saints.

The three, who are or have been members of the church, are connected to the community of Bountiful in southeastern British Columbia, where the trial heard plural marriage was practised.

The charges against the Blackmores centred on records that show the 13-year-old girl was married to Warren Jeffs, the 60-year-old church prophet 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.

Much of the evidence heard in the judge-only trial came about as a result of a U.S. investigation into Jeffs.

Special prosecutor Peter Wilson drew on records found locked away in a Texas ranch during the trial in an effort to prove the girls' marriages took place within days of the accused receiving instructions from Jeffs.

Wilson also focused much of his case on how sex and marriage were viewed in the church. The court heard from former members who said women were expected to obey their fathers and husbands, have as many children as possible and never turn away their husbands' sexual advances.

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 and Oler did not have a lawyer during the trial, so an impartial adviser was appointed to assist the court and provide balance. They did not give opening or closing arguments for themselves.