Three followers of a polygamous sect accused of taking girls across the border could have foreseen that sexual contact with older men would be a likely consequence of their actions, a special prosecutor told a British Columbia judge on Monday.

Peter Wilson delivered closing arguments at the B.C. Supreme Court trial for Brandon Blackmore, Gail Blackmore and James Oler, who are charged with removing girls from Canada for a sexual purpose.

Brandon and Gail Blackmore, who are separated as "celestial" husband and wife, each face a charge related to a 13-year-old girl who church records show in 2004 married Warren Jeffs, the now-imprisoned prophet of the Fundamentalist Church of Jesus Christ of Latter-Day Saints.

Cross-border investigation

Records admitted into evidence at the trial show Jeffs told Brandon Blackmore the girl "belonged" to him.

Wilson described co-accused Gail Blackmore as a "willing participant" in the girl's marriage to Jeffs.

Jeffs, now 60, was convicted in 2011 and sentenced to life in prison plus 20 years in the United States for sexually assaulting two girls he claimed were his "spiritual" wives.

Crossfield and Blackmore

Emily Ruth Gail Blackmore, also known by the last name Crossfield, enters the Cranbrook courthouse on Tuesday Nov. 22 with her co-accused, Brandon James Blackmore. (Bob Keating/CBC)

Much of the evidence in the case against the Blackmores and Oler came about through a U.S. investigation into Jeffs. All three accused are connected to the polygamous community of Bountiful, B.C.

Wilson told the court that border records from late February 2004 show the Blackmores and another woman crossed into Idaho, but the 13-year-old girl was "conspicuously absent."

He said the girl must have crossed the border somehow because days after the Blackmores were given orders by Jeffs, priesthood records show the polygamous leader married the teen.

Wilson added that it's not necessary for the prosecution to prove the defendants acted with "motive or desire" that sexual activity take place between Jeffs and his young bride, but only that they could foresee that happening as a result of the marriage.

Charges involve a 15-year-old girl

The judge heard earlier in the trial about the beliefs around sex and marriage in the church from former members of the sect.

Women were required to be obedient to their fathers and husbands, and plural marriage was a key tenet of the religion. Women were to bear as many children as possible, the trial heard.

Witnesses said sex was not to take place before marriage, but as soon as possible after the ceremony. The court heard the sole purpose of sexual intercourse for the church's members is procreation, and women are not allowed to turn away their husbands' advances.

"All of these things lead to the inference that sexual contact between (the 13-year-old) and Warren Jeffs was a certain or substantially certain consequence of marriage," Wilson said.

The charge against Oler centres on a 15-year-old girl married to James Leroy Johnson in 2004.

Wilson described for the court how instructions from Jeffs on transporting the girl to the Unites States were "carried out to the letter."

He told the court Oler would have been able to foresee that the girl was being forced into a relationship with an authority figure or someone on whom she'd be dependent.

'The priesthood head is the boss'

The court heard throughout the trial how women were to obey their "priesthood head," their fathers before marriage and their husbands after.

The former members testified that women in the community were not able to possess their own assets or pursue an education without permission.

As a result, women depend economically on their husbands, making it difficult to break free, Wilson told Justice Paul Pearlman, who has heard the evidence without a jury.

"The priesthood head is the boss. It's something that's taught from Day 1," said Wilson.

Pearlman ruled earlier in the trial that priesthood records dictated by Jeffs and found in a secure vault on a church ranch in Texas are trustworthy and can be used in the criminal proceedings of the three accused.