The issue that will not die!
Bill's 2024 post is essentially correct.
I can cheerfully stipulate that seemingly critical items of evidence MIGHT have been ruled inadmissible at a criminal trial and that Oswald MIGHT have been found not guilty. And so what?
Once again: The point of a criminal trial is to determine whether the prosecution can meet its burden of proof that the accused is guilty. The purpose is not to determine "what really happened" or to write history.
As Bill suggests, before moving to introduce evidence at trial the prosecution would have recognized any defects in the chain of custody and attempted to rehabilitate them with testimony at trial. The judge could either find the defects fatal and rule the evidence inadmissible or allow the evidence while instructing the jury that the defects could be considered in weighing its probative value.
History is not bound by legal niceties. There are no formal burdens of proof, rules of evidence or rules of procedure. Historians - and us, as laymen - simply assess the evidence as we have it, warts and all. Ditto for the WC. If we think they erred in their admission and evaluation of evidence, that's fair game for discussion.
But outside the context of a criminal trial, squawking about "chain of custody" and "admissibility" is just a distraction, a red herring.
The issue that will not die!