Pretty damaging evidence, from a This Rock article :
From a very early date, the relatives and acquaintances of a retired Congregationalist minister, Rev. Solomon Spalding, who died in 1816, had complained against the Latter-Day Saints that the Book of Mormon was really a plagiarized version of an unpublished novel, Manuscript Found, which the deceased clergyman had written and circulated among his friends. A number of affidavits were sworn to this effect, but their publication and propagation was sporadic and poorly organized. The LDS church launched a massive counterattack that capitalized on the fact that the original draft of Manuscript Found could not be produced to verify the affidavits.
Naturally, the Mormons claimed that these were malicious, satanically inspired falsehoods. All that remained was an earlier Spalding novel, Manuscript Story, which shows some definite stylistic similarities to the Book of Mormon but also some marked differences. Eventually, most anti-Mormon writers stopped appealing to the Spalding theory as an explanation for the Book of Mormon because the available evidence seemed incapable of being substantiated.
But Cowdrey, Davis, and Scales pieced together a long chain of events connecting Smith and Spalding. The chief link in the chain was an itinerant evangelist named Sidney Rigdon, who had a close friend who worked at the print shop in Pittsburgh, Pennsylvania, from which Spalding’s second manuscript disappeared. A Dr. Winter later claimed to have been shown the manuscript by Rigdon in 1822.
Rigdon was eventually baptized into the Mormon Church in November 1830 and always claimed that he had known nothing of Smith or Mormonism until late that year. Cowdrey et al found at least ten people who testified that they had seen Smith and Rigdon together a number of times from 1827 onwards—the very period when Smith was preparing the Book of Mormon.
The climax came in 1976 when Cowdrey and his friends were examining some old manuscripts in an LDS church library. They came across a few pages from the Book of Mormon in handwriting no one had been able to identify. But before this the researchers had managed to track down some undisputed samples of Spalding’s handwriting at Oberlin College in Ohio, including a deed from January 1811 bearing his signature.
There, amid the quiet and rather dull surroundings of paper and bookshelves, the awesome truth dawned on them: These harmless-looking scraps of aging paper had the potential to shatter once and for all the myth of Joseph Smith the saint and prophet—a great, historic, American myth for which men and women had lived and died and suffered and killed; a myth that had pioneered part of the Wild West, built the state of Utah, and now ruled the hearts and lives and fortunes of millions round the world.
This extract from the Book of Mormon (“translated” from “golden plates” in 1828) was in the handwriting of Solomon Spalding (died 1816)! What the young men had stumbled on was part of the long-lost manuscript of Spalding’s second novel—crushing evidence of Smith’s plagiarism and deceit that had been preserved by the unsuspecting Mormons themselves.
The three men proceeded to write a book detailing the results of their research (Who Really Wrote the Book of Mormon? Vision House Publishers, 1977). The LDS Church issued denials of the identification and prohibited any further examination of the relevant manuscript. But the detailed testimonies of two independent handwriting experts, William Kaye and Henry Silver, are photographically reproduced for all to see: the unquestioned Spalding documents and the supposed Book of Mormon extract are judged professionally to be definitely in the same hand (Walter Martin, The Maze of Mormonism, pp.62–64).[/FONT]