In this particular case (which is what my earlier question to you is based on) there are no legal provisions for a trial for a dead man. Therefore, your idea of a proper legal setting is improper and not legal. This makes your claim false and irrelevant.
Yes and yes. But you have to repeat this several times for it to be understood. If you're lucky.
But let me play lawyer and point out that even this proposed "legal setting" doesn't necessarily find the truth since, after all, it's not designed to. The court/legal standard or adversarial process is designed to find, based on the decision of a jury of the defendant's peers, whether the government has proven, using the law, beyond a reasonable doubt that a person has committed a crime. It's not designed to discover the truth. As we know, lots of innocent people have been convicted; lots of guilty people have been found not guilty. It's the best system we can come up with; but it's not perfect and finding the "truth" is not the goal.
The Oswald defenders, for some unknown reason, want to use this legalistic standard - "chain of custody" and other legal rules - to throw out the evidence against him. If they were interested in the truth, in what really happened, they wouldn't engage in these defense lawyer like tactics. But here we are. And here they are.