Well, yes, strictly speaking. Point well taken.
But I think the totality of circumstances including number of GSWs, officers carrying back up guns that are 9mm, and Joe claiming - no, insisting - he fired once, I think the finding of an odd ball live 9mm round likely goes to a gun. I take Joe at his word (no choice right now and no evidence to the contrary) that he himself does not carry a back up gun in accordance with the agency's prohibition. He's a former marine sgt. and does play by the rules. He's not an angel, but he's a very honest and sincere person. (I know that means nothing in a court of law or to the I A cops.)
No one I know, especially coppers, carry just bullets without a gun. I'm fairly certain bad guys don't. Its not like, Oh, gee, a bullet just fell out of my pocket. This is a shooting scene. This part of Joe's beat, while it borders a sort of run down part of the city I worked in, is not known for shootouts or gunplay.
Based upon what I've gotten from you guys I just am curios to find out what, if any, tests were done on this live round? Was it recently ejected? Was it pristine as if someone just plucked one from a fresh box of ammo and dropped it there? Is there DNA? Fingerprint?