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William E. M'Lellin
William E. M'Lellin was born January 18, 1806, in Smith County, Tennessee. William first heard about The Church of Jesus Christ of Latter-day Saints in 1831 from David Whitmer, one of the Three Witnesses of the Book of Mormon. William had been working successfully as a teacher, but soon left that job to travel to Independence, Missouri, to learn more about Mormonism. He wrote on August 20, 1831, “I…betook myself to earnest [prayr] to God to direct me into truth; and from all the light that I could gain by examinations searches and researches I was bound as an honest man to acknowledge the truth and Validity of the book of Mormon…” 
Following his baptism by Hyrum Smith, William traveled to Ohio so he could meet Joseph Smith. After meeting the Prophet, William prayed in secret on some specific questions in his mind. He then asked that Joseph pray to the Lord concerning him. In the revelation that followed, all of William’s specific questions, of which he had not told Joseph Smith anything, were answered.
Despite his own confirmation of the Book of Mormon and his personal answer from the Lord through Joseph Smith, William still criticized the language of the revelations that were received. Through Joseph Smith, the Lord challenged the most wise among them to imitate the revelations. William took the challenge and Joseph Smith recorded, “William E. M’Lellin, as the wisest man, in his own estimation, having more learning than sense, endeavored to write a commandment like unto one of the least of the Lord’s but failed.” 
William served a mission in Missouri and Illinois in 1832 and on February 15, 1835, was called as a member of the Quorum of the Twelve Apostles. His faith in the Church and his position in the Quorum did not last long. William wrote a letter censuring the First Presidency and had apostatized by 1836. He was excommunicated in 1838.
William did not leave the Church peacefully. He participated in mobbing and robbing the members of the Church in Missouri. When Joseph Smith and other leaders were being held in Richmond, he appeared requesting the Sheriff for permission to flog the Prophet. He received permission if Joseph was willing to fight. Joseph agreed he would if his irons were taken off. Upon hearing this, M'Lellin required a club, and although Joseph Smith was still willing to fight, the Sheriff refused a fight on such unequal terms. 
William joined with Martin Harris in Kirtland in 1847 to organize a new church called The Church of Christ. David Whitmer was asked to be the church’s prophet, but the sect didn’t last past 1849. Despite his disbelief in The Church of Jesus Christ of Latter-day Saints, William never faltered in or denied his testimony of The Book of Mormon.
He died April 24, 1883, in Independence, Missouri.
Bibliography: Susan Easton Black, Who’s Who in the Doctrine & Covenants, pg. 190-193.