The simple answer is that witnesses can lie or be mistaken and often the only way to tell is to ask questions to clarify their testimony or to catch them making inconsistent statements that would indicate either fabrications or faulty recollections or perceptions. This is also why eye witness testimony is not considered very strong; it is very often wrong. The most important evidence in a court is factual, forensic evidence such as DNA or fingerprints, not eye witness testimony.
Before publishing the Book of Mormon to the world Joseph Smith had 11 witnesses sign statements attesting to its divine origins. First there were 3 witnesses and then later 8 more. Their testimonies can be found at the front of every Book of Mormon that has ever been published and are linked in the previous sentence. If you haven't ever read them, then you probably should. If they are to be trusted and their testimonies are true then the Book of Mormon is the word of God even more surely than the Bible or any other book known and you ignore it and the Mormons at your eternal peril.
So, why don't I believe them? This is most assuredly the strongest piece of evidence that the church has in its favor. None of the witnesses ever renounced their testimony and throughout their lives repeatedly reaffirmed by word and deed their belief in the Book of Mormon as the word of God even though some repudiated Joseph Smith as a fallen prophet and Brigham Young and his polygamist followers as apostates.
First let's look at what they actual testified. The 3 witnesses state the following:
- They saw, through the grace of God, the gold plates.
- The voice of God declared to them that the plates were translated by the gift and power of God.
- They saw the engravings that were on the plates.
- They were shown to them by the power of God and not of man.
- An angel came down from heaven and showed them the plates and engravings.
- The voice of the Lord commanded them to bear record of it.
- Joseph Smith showed them the plates.
- They had the appearance of gold.
- They handled the leaves that Joseph translated.
- They saw the engravings which appeared ancient and of curious workmanship.
- They hefted the plates.
So, again, why don't I believe them?
Let's start with the 3 witnesses. If the plates physically existed then why did an angel have to bring them and why was the power of God required to see them and inspect them? In later accounts Martin Harris gave a curious account of how he obtained the witness and it hardly makes his witness very believable. It is clear that the experience was in his head, or as believers would have it, spiritual. David Whitmer later confirmed that the testimony was based on a spiritual experience. This caused him no pause, but it make me wonder why physical plates rely on what has proven to be highly suspect "spiritual" experiences. People, Harris and Whitmer among them, believe strongly in the trustworthiness of such experiences, but evidence shows otherwise.
Other than Martin Harris, why didn't the witnesses subsequently talk about the particular circumstances of seeing the plates? What were the dates and places? Did they see them individually or in a group? Was the lighting good? Did they all see the same details? Were they in a visionary state when they saw them? Were the characters engraved deeply? Were the engravings thick or thin? Were both sides of the plates engraven or only one side? How were they bound? What size were they? How thick were they? How much did they weigh? How was the sealed portion sealed? Were they smooth or rippled? Did they show signs of age?
There are so many questions that could be asked, but from what I can tell, if they were ever asked these questions they weren't answered. Given the church's fondness for its history, if these details existed I'm sure that I'd have heard them during my years of Sunday School, seminary, institute, missionary service, and church meetings. Instead, what I know of are pro forma responses that basically say, "We confirm our written testimony." That in and of itself seems very suspicious.
When lawyers cross examine a witness they look for signs of memorized or prepared testimony. If the witness repeats exactly the same thing over and over again it starts to sound suspicious like they have been told what to say. The 11 witnesses' testimonies seem to fall into this category. In fact, the testimonies were prepared by Joseph Smith. Martin Harris claimed that the 8 witnesses also saw the plates only with their spiritual eyes and that some were hesitant to sign the prepared statement.
So, do I believe them? As far as I can tell, they are testifying to what they saw in a dream-like state. So, I believe that they are telling the truth. But I don't believe that what they saw in vision actually existed. Otherwise they wouldn't have needed to be in a vision.
Do I belive the gold plates ever existed or that the Book of Mormon is a translation of them? Nope. The evidence is strongly against it and the dreams or visions of 11 witnesses won't change that.