"I believe" I doubt", these are all expressions of whatever prejudices we have. You need to examine the evidence to try to make a sensible diagnosis. Unfortunately, the evidence is so corrupted by the ease of producing photographic images or plausible testimony, and by the motivations of unreliable witnesses, that sensible diagnosis is virtually impossible - first person eye-witness evidence is all you can rely on, and that can't be relied on too much unless it is absolutely stunning and in defiance of other explanation. And, of course, you might just be a nutter, so you can't win, really.