Here is a brief write-up on the 3 witnesses. You can find the full article here:
http://www.irr.org/mit/bom-wit-pt1.htmlWhile Joseph Smith was dictating the Book of Mormon to Oliver Cowdery, he read off a section that declared there would be three special witnesses who would be allowed to see the plates and then "bear witness" to the Book of Mormon. Joseph Smith's History of the Church states:
Almost immediately after we had made this discovery, it occurred to Oliver Cowdery, David Whitmer and the aforementioned Martin Harris (who had come to inquire after our progress in the work) that they would have me inquire of the Lord to know if they might not obtain of him the privilege to be these three special witnesses; and finally they became so very solicitous, and urged me so much to inquire that at length I complied (History of the Church, Vol. 1, pp. 52-53).
Joseph then produced a revelation for Oliver, David and Martin which stated that if they relied upon God's word and did so with a full purpose of heart they would "have a view of the plates, and also the breastplate, the sword of Laban, the Urim & Thummim ... and the miraculous directors which were given to Lehi" (Ibid, p. 53). It would only be by their faith that they would be able to obtain a view of them.
This is very convenient. Joseph dictates the part of the Book of Mormon that mentions three special witnesses while all three are there with him. These men beg Joseph to ask God if maybe they aren't the ones. When he finally gives in, Joseph immediately gets a revelation that says, if they have faith, rely on God's word and have full purpose of heart, they will see not only the plates but numerous other wonderful things.
So they go to the woods and first spend a prolonged time in prayer. Nothing happens. They pray more. Nothing happens. Martin Harris volunteers to leave the group because he senses the others think he was the reason nothing was happening. As soon as Harris leaves, the others claim to see the angel and plates, though there is no mention of any of the other items that had been promised. According to Joseph Smith's history, Joseph then goes to find Harris, and while praying together, Harris cries out, "Tis enough, tis enough; mine eyes have beheld; mine eyes have beheld;" (Ibid, p. 55). It becomes clear that all three of these men desired this prestigious position of being the special chosen witnesses. They were emotionally primed by what Joseph claimed to translate and then by the revelation Joseph gave that emphasized their need for faith. The vision only came to Oliver and David after a prolonged time in prayer and the departure of Martin Harris.
It would appear from this account and Doctrine & Covenants 17, that the idea of three witnesses to the Book of Mormon is a new discovery made by Joseph and Oliver in June of 1829 while producing the Book of Mormon. Yet, three months earlier in March of 1829, Joseph received a revelation for Martin Harris which stated that Joseph had the gift to translate the Book of Mormon but that God would grant him no other gift, and that God would call and ordain three special witnesses to whom God would give supernatural power to "behold and view these things as they are." The revelation went on to say that no one else but the three would have the power to receive this same testimony. It is possible that Joseph did not refer back to this March 1829 revelation regarding the witnesses because by June he already had in mind to add eight additional witnesses besides Cowdery, Whitmer and Harris. Adding additional witnesses would go against the earlier revelation that there would be three and only three witnesses and that Joseph should not show the gold plates to anyone else (D&C 5:3, 12-14).
Also, in an interview Martin Harris was interviewed by Anthony Metcalf:
"I never saw the golden plates, only in a visionary or entranced state. I wrote a great deal of the Book of Mormon myself, as Joseph Smith translated or spelled the words out in English. Sometimes the plates would be on a table in the room in which Smith did the translating, covered over with a cloth. I was told by Smith that God would strike him dead if he attempted to look at them, and I believed it. When the time came for the three witnesses to see the plates, Joseph Smith, myself, David Whitmer and Oliver Cowdery, went into the woods to pray. When they had engaged in prayer, they failed at the time to see the plates or the angel who should have been on hand to exhibit them. They all believed it was because I was not good enough, or in other words, not sufficiently sanctified. I withdrew. As soon as I had gone away, the three others saw the angel and the plates. In about three days I went into the woods to pray that I might see the plates. While praying I passed into a state of entrancement, and in that state I saw the angel and the plates." (Anthony Metcalf, Ten Years Before the Mast, n.d., microfilm copy, p. 70-71.)
I believe the lack of archeological evidence, the DNA testing of the American Indians, and the heretical gospel taught in the Book of Mormon substantiate that the Book of Mormon was written by J Smith and not received by revelation as he pretended.