Take the stand. Trespassing is a serious offense, and I would bet that it was no accident, this person knew he was trespassing. I would also bet that if they are willing to trespass they would also take something from your land without asking.
I get really bent out of shape on this subject because we have some family land and have dealt with these problems for years. I can't stand a liar or a thief and usually the two run hand in hand (trespassers included).

My 2 cents.

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