If each piece of evidence is false, the evidence cannot be independent. They cannot all be false by random chance.
So the falsity has to have a common cause. This means there must be a huge conspiracy involving all levels of officials engaged in evidence planting, evidence gathering, evidence preservation and witness tampering If there was evidence of widespread falsification and some coherent reason so many people would not only agree to be involved but would agree to remain silent for 60 years, one would be inclined to have a look at that. But there is not. Nothing. Zero.
I would agree that in any random run of mill conspiracy it's unlikely that people remain silent. There are all sorts of reasons why the individuals involved in such a conspiracy, at some point in time under certain circumstances, would be prepared to talk.
However, if this was a conspiracy, it's hardly a run of the mill case. All sorts of special circumstances come in to play, especially if high ranking powerful people were indeed involved. Take for instance the military service personal who were present at the autopsy, who were given an order not to discuss what they had seen and knew with anybody on punishment of a court martial. They all kept quie for some fifteen years, until they were given special permission to talk to the HSCA investigators and some of them still were hesitant to talk and not without cause as those who did talk were instantly attacked and ridiculed by WC defenders. It happens nearly every day that witnesses don't want to come forward because they simply do not want to be involved in a criminal matter and/or they fear for the possible consequences. Then of course there were people who performed a minor task without even realizing they were part of a conspiracy, who simply never came forward because of fear or a simple lack of understanding of their involvement. Imagine being a private individual with a story to tell, but that would mean going up against the US Government. Would you tell your story nevertheless? Others were given orders by their superiors to perform a task and not mention it to anybody, like, for instance, Hosty who was told by Shanklin to destroy a note written by Oswald which obviously is destruction of evidence. And let's not forget individuals like Tomlinson who received a phonecall from an FBI agent who told him to keep his mouth shut.
So, it's simply too easy to say that there was no conspiracy because somebody would have come forward after all this time.
