More on William Smith-
“And William Smith has asserted that I was the cause of the death of his brother Samuel, when brother Woodruff, who is here to day, knows that we were waiting at the depot in Boston to take passage east at the very time when Joseph and Hyrum were killed. Brother Taylor was nearly killed at the time, and Doctor Richards had his whiskers nearly singed off by the blaze from the guns. In a few weeks after, Samuel Smith died, and I am blamed as the cause of his death.” – Prophet Brigham Young, July 1857, Journal of Discourses, vol. 5, p.77A.
Check of church history sources reveals theses clues:
“Samuel Harrison Smith, born in Tunbridge, Vt., March 13, 1808. Died July 30, 1844, broken hearted, and worn out with persecution. Aged 36. The righteous are removed from the evils to come.” – Times and Seasons, Vol.5, No.24, p.760
“Hyrum & Joseph was Murdered Carthage Jail in Hancock Co[,] Illinois. Samuel Smith died in Nauvoo, supposed to have been the Subject of Conspiracy by Brigham Young.”- Joseph Smith Family Testimony, William Smith Notes Circa 1875, Vogel, Early Mormon Documents, p. 488.
Why would such an accusation be laid against Brigham Young? To understand the context, you have to remember that after Smith and Hyrum were killed, there was some conflict over who should be his successor. Brigham Young was not in Nauvoo when Smith was killed, but started to head back as soon as he heard the news. Meanwhile in Nauvoo, several potential leaders were positioning to take the reins of leadership. The most popular replacement was Samuel Smith, the brother of Joseph Smith. William Clayton had recorded Joseph declaring his brother William his successor if both he and Hyrum were killed. But Brigham Young’s first cousin and church apostle, William Richards insisted that nothing should be decided until Brigham Young could return to Nauvoo. However, many members did not want to wait, and more and more support was gathering behind Samuel Smith, Joseph Smith’s brother, to become the next Prophet and leader of the church. For a select few, this presented a problem because Samuel was violently against polygamy. It was looking like Samuel Smith would become the next prophet and promised to denounce the practice of plural marriage.
D. Michael Quinn, The Mormon Hierarchy: Origins of Power, p.152-153:
“Then Samuel Smith suddenly became violently ill and died on 30 July 1844. This added suspicion of murder to the escalating drama. Council of Fifty member and physician John M. Bernhisel told William Smith that anti-Mormons had somehow poisoned his brother. William learned from Samuel’s widow that Hosea Stout, a Missouri Danite and senior officer of Nauvoo’s police, had acted as his brother’s nurse. Stout had given him “white powder” medicine daily until his death. Samuel became ill within days of the discussion of his succession right, and by 24 July was “very sick.” There had been enough talk about Samuel’s succession claims that the newspaper in Springfield, Illinois, reported: “A son of Joe Smith [Sr.] it is said, had received the revelation that he was to be the successor of the prophet. “”William Smith eventually concluded that Apostle Willard Richards asked Stout to murder (his brother) Samuel H. Smith. The motive was to prevent Samuel from becoming church president before Brigham Young and the full Quorum of Twelve arrived (in Navuoo). William’s suspicions about Stout are believable since Brigham Young allowed William Clayton to go with the pioneer company to Utah three years later only because Stout threatened to murder Clayton as soon as the apostles left. Clayton regarded Hosea Stout as capable of homicide and recorded no attempt by Young to dispute that assessment concerning the former Danite.”” One could dismiss William Smith’s charge as a self-serving argument for his own succession claim, yet Samuel’s daughter also believed her father was murdered. “My father was undoubtedly poisoned,” she wrote. “Uncle Arthur Millikin was poisoned at the same time-the same doctors were treating my father and Uncle Arthur at the same time. Uncle Arthur discontinued the medicine-without letting them know that he was doing so. (Aunt Lucy [Smith Millikin] threw it in the fire). Father continued taking it until the last dose-he spit out and said he was poisoned. But it was too late-he died.” Nauvoo’s sexton recorded that Samuel Smith died of “bilious fever,” the cause of death listed for two children but no other adults that summer.” “This troubling allegation should not be ignored but cannot be verified. Nevertheless Clayton’s diary confirms the efforts of Richards to avoid the appointment of a successor before his first cousin Brigham Young arrived. Stout’s diary also describes several occasions when Brigham Young and the apostles seriously discussed having Hosea “rid ourselves” of various church members considered dangerous to the church and the apostles. Stout referred to this as “cut him off-behind the ears-according to the law of God in such cases.” Stout’s daily diary also makes no reference whatever to his threat to murder Clayton in 1847. When the Salt Lake “municipal high council” tried Hosea Stout for attempted murder, he protested that “it has been my duty to hunt out the rotten spots in the Kingdom.” He added that he had “tried not to handle a man’s case until it was right.” Evidence does not exist to prove if the prophet’s brother was such a “case” Stout handled.”