The brown shirt that Oswald took off at his boarding house was one of TWO brown shirts he had. The 2nd one, he put on, having same type of fiber and color as the 1st brown shirt, could NOT have been at TSBD during the shooting, so any test results from that 2nd shirt is of no value to prove the MC rifle was in Oswalds hands being fired at the TSBD on Nov 23/63
and a test of BOTH shirts producing SAME approximate characteristics might be something to consider, in regard that it would show that ANY shirt of same type could have been worn by someone else as much as by Oswald and fiber from THAT shooters shirt would ALSO match Oswalds shirts and could have been left on the MC rifle just the same.
Neither shirt as far as i am aware had any signs of gunpowder residue, neither from MC rifle nor the revolver. The jacket also, no gunpowder residue was stated found. Yet the paraffin test on Oswald's hand was positive.
Nowadays, the perspiration left in the shirts could be analyzed by DNA test and linked to whomever wore the 1st shirt, but I guess that would not be possible 56 years later to conduct a DNA test of the 2 shirts Oswald supposedly wore that day of Nov 22/63?