a .25-caliber shell casing was discovered in melvin's barn, and ron harshman purchased a .25-caliber handgun just a few weeks before melvin disappeared. but ron was never able to produce the weapon, saying it had been misplaced. >> there was a lot of information there, but nothing new was coming in to give you the opportunity to do anything more with it. >> nelson pored over the case file and discovered an interesting notation. ron harshman admitted test firing his new .25-caliber pistol in his backyard just after buying it. that gave nelson an idea. >> what about going out there and seeing if we can find a shell casing and then compare that to the one in the barn. >> when mr. nelson originally