He is accused of marrying 24 women, and Oler allegedly has four wives.
Jane Blackmore told the court that she grew up in the Fundamentalist Church of Jesus Christ of Latter-Day Saints. That group broke away from the Salt Lake City-based Church of Jesus Christ of Latter-day Saints at the turn of the 20th century. Unlike the FLDS, the Salt Lake City church officially abandoned polygamy in 1890 and excommunicates members found practicing it.
After pressure from her father, Jane Blackmore agreed to be married and was taken to see a prophet who would determine a husband for her based on divine instruction.
Jane Blackmore said she learned at 10:30 p.m. on May 3, 1975, that her husband would be Winston Blackmore. They were married at 9 a.m. the next day.
Jane Blackmore told the court that she knew other wives were likely to follow because the FLDS faith dictates that a man must have three wives to advance in the church and attain the highest level of celestial glory.
Blackmore said she was sometimes asked to approve the marriages, but there were other unions she didn't learn about until after the ceremony had occurred.
She testified that there was one instance where a young woman who was marrying Winston Blackmore traveled up from the United States with her younger sister.
Jane Blackmore told the court that the man conducting the ceremony claimed divine inspiration and married both sisters to Winston Blackmore.
Jane Blackmore left Bountiful and her relationship with Winston Blackmore in 2003, but testified that her former husband married over 25 women during the course of their relationship.
She also testified that Oler, her brother, had multiple wives and that she had attended the births of children he had with two of those wives.
The criminal trial has been more than 25 years in the making, with RCMP first investigating allegations that residents of the isolated, religious community were practicing plural or "celestial'' marriage in the early 1990s.
The trial is being heard by a judge alone and is expected to last at least two weeks.