Apparently you missed the post earlier in this thread that shows that the FBI lab DID in fact examine Lee's shirt ( the one that he was wearing at the TSBD that morning, the one with the button down collar) If they had found gun powder residue on that shirt ( as they certainly would have if he had fired a gun) they would have published that information in bold headlines.
Here's Pat Speer's post......
William, I contacted the Archives a few years back and asked for its help in determining if the light brown shirt they had in their collection was in fact the "reddish" shirt Oswald claimed he'd been wearing on the day of the shooting. After months of haggling, and working out the financial details (I had to pay them), they sent me some hi-res color photos of the shirt, which turned out to be reddish. One of these is presented above.
As shown on my website, moreover, one of the photos they sent me showed the inner collar of the shirt, and the initials of a multitude of FBI experts. This led me to believe that yessiree the shirt was tested for nitrates among other things and that the results of these tests were kept from the public. (There is no published report discussing any tests performed on this shirt.)
I had read Pat's analysis that the shirt had been tested and had made a point as regards the lack of forensic evidence in a previous post.
My question to SMG was that he needs to explain how LHO can fire a rifle and leave no forensic evidence on his clothes.
He may have a good explanation as to how this can happen and I am sure everyone would be interested in hearing it.