And even if the chain of custody is a mess, that does not itself actually invalidate item evidence.
As the chain of custody is one of the main ways to authenticate a piece of evidence. Without authentication, how can you still consider an item valid evidence?
As usual you're missing the point, in the case of the revolver.
Oswald was arrested while carrying the revolver.
Oswald admitted to carrying the revolver.
Oswald ordered the revolver.
The revolver in evidence is the exact same revolver that he purchased.
Oswald being in a bind about the rifle being mail order, simply made up a fictitious Fort Worth origin for the revolver.
Besides as I said yesterday, why swap a revolver that is extremely difficult to match the expended bullets with another revolver that is extremely difficult to match the expended bullets, that only makes sense in the Bizarro World of CT's.
JohnM