Three young teenaged girls from Bountiful, B.C., were moved to the United States and married to a jailed American polygamous leader at the ages of 12 and 13, the provincial government alleges in newly filed court documents.

The B.C. government has applied to introduce last-minute evidence at a case examining the constitutionality of Canada's anti-polygamy law, which formally wrapped up evidentiary hearings earlier this month. Closing arguments are scheduled for the spring.

The province says it has obtained documents from authorities in Texas that indicate three girls from Bountiful were married in 2004 and 2005 to Warren Jeffs, who leads the Fundamentalist Church of Jesus Christ of Latter Day Saints, also known as the FLDS.

The FLDS is a breakaway Mormon sect, which, unlike the mainstream church, continues to practise polygamy.

An affidavit filed with the court says a 13-year-old girl was married to Jeffs, who was 48 at the time, in Colorado City, Ariz., in 2004. It notes that the child's parents participated in the so-called celestial marriage.

Then in 2005, the affidavit alleges, two 12-year-old girls were married to Jeffs on separate occasions in Arizona, before they were taken to an FLDS compound in Texas.

The documents stem from a raid on that compound, known as the Yearning for Zion ranch, in 2008.

Texas authorities seized more than 400 children, most of whom were eventually returned to their families. Seven men were convicted of child sexual assault and abuse.

Jeffs faces trial in Texas on child sex assault and bigamy charges, and may face a second trial related to the marriage of underage girls in Utah.

"All three of the children may be the victims of serious crimes," the B.C. government says in its application to include the new evidence.

A hearing has been scheduled for next Friday to determine whether the late evidence can be admitted.

The court spent more than two months hearing evidence from academics, former residents of polygamous communities and current plural wives as it weighs the alleged harms of polygamy.

The provincial and federal governments must prove that polygamy, on its own, is inherently harmful if they hope to uphold the law.

Those alleged harms include child brides and teenage pregnancies, with young girls being married off to much older men.

The marriages of the three girls to Jeffs would add to evidence that, until recently at least, teenagers in Bountiful were routinely married well before they reached the legal age of consent.

The FLDS adopted a policy in 2008 that only women 18 and older would be married. Provincial birth records suggest teen pregnancies in Bountiful stopped after that policy was inacted.

The court also heard allegations that young girls have been trafficked between Bountiful and polygamous communities in the United States.

Three women currently living in Bountiful testified anonymously, and one of them told the court that when she was 17 and living in the United States, she married a Canadian man and moved to Bountiful. Another American girl, who was 15, joined the family a few months later. Their husband was in his 40s.

The province launched the constitutional reference case after the failed prosecution in 2009 of Bountiful's two leaders. Winston Blackmore and James Oler were each charged with one count of practising polygamy, but those charges were later thrown out on technical legal grounds.

The men each lead separate divided factions within Bountiful. Blackmore has boycotted the hearings because he was denied government funding, while Oler, whose congregation is participating, initially offered to testify but later changed his mind.