>> kevin was a suspect that we needed to find out the validity of his statements, whether he had gunshot residue on his hands, whether he was even able to shoot a gun, given his physical disabilities. >> reporter: but a suspect? they checked his hands for gun powder residue. negative. >> you have to look at everybody, unfortunately. sometimes hurts feelings, but you have to get down to the facts, too. >> reporter: but facts can be tricky things. and in this case far more elusive than anyone might have imagined. some clues were elusive but some were right out in the front, like the two that dramatically narrowed down the circle of suspects. >> coming up. >> those are huge. you eliminate everyone down to except those who have access to those two keys. >> when "deadly trust" continues. hen "deadly trust" continues. [ laughing ]