Not a one of them has any credibility.
The retired Army Lieutenant Colonel of Special Forces is the most credible witness I've ever seen interviewed.
One the most credible to me was a man stopped at the side of a freeway overlooking Dealy Plaza. He had a side-on view down the length of the "grassy knoll" fence. He was also a deaf mute with nothing to gain. His testimony was never given much credibility by the authorities, most likely because of his disability. To me, his coming forward despite knowing he would be marginalized or ridiculed lend him far greater credibility than some government agent or politician.