the bicycle tire, that's the tire that's on 80% of all the mountain bikes in the u.s. it's the most common tire. so there's nothing very distinctive about that. they wanted to be able to tell the jury that it was a match. they were not allowed to do that because as the experts said, "we have no idea if it's a match or not." >> something that has more or less. >> reporter: the defense called its own forensic pathologist to ask if the medical examiner was correct in his conclusion that the murder weapon was a golf club. >> with regards to saying, ah, specifically this weapon, i can't. >> i think the golf club is a, as alfred hitchcock used to say, it's the mcguffin, okay? it's the magic device to tie it to steve democker, the golfer, the elitist. >> sure. >> the rich guy who is pissed off about. >> fine. but isn't there scientific evidence to say that's a golf club head that hit it? >> no. i don't agree with any of that. and nobody, not a single person