Even [minor participants] are inflating their roles for ego, profit, or a place in history.
The same has become true for 9/11 and has been generally true for UFO reports. Minor participants, standers-by, and just plain imposters have fabricated or embellished reports in order to amplify their association with noteworthy events. This is a problem all historians have to face.
How in the world, a half century later, are we supposed to judge fact from fiction?
The same way we've always done: with a sober and dispassionate approach to the evidence, and a good dose of skepticism and critical thinking. And no, "skepticism" doesn't necessarily mean always doubting the "official story." In fact, even the term "official story" bespeaks the belief of some conspiracy theorists in a shadowy, omnipotent Ministry of Truth that concocts what the masses are intended to believe.
It's not perfect, but it leads to one inexorable conclusion, that Lee Oswald, with his rifle, shot and killed JFK from the Depository.
The most credible story doesn't have to be perfect. No story in history is free from inaccuracy, misattribution, embellishment, inconsistently, and incompletness. The most credible story has to be the one, among all those that are plausible, that explains the
most evidence with the
least loose ends.
Conspiracy theories rarely compete well. The evidence they seek to explain is generally the outlying or misunderstood, misperceived evidence -- and they explain it only at the egregious expense of the majority of central evidence. That's why conspiracy theories generally acknowledge that there's a wealth of evidence in favor of the common belief, but that it has all been doctored, faked, or otherwise compromised. It's a tortured tale that amounts essentially to "All the evidence points here, but I'm going to believe something else." All the wild unsupported accusations of forgery and tampering are
loose ends.
A good rule of thumb for viable analysis is that it's going
toward something rather than
away from it. Most conspiracy theories start by trying to discredit the "official story." They pick at it, kick holes in it, try to show that it's somehow suspiciously incomplete, and identify "inconsistencies" and "anomalies" in it that they say make it hard to believe. This is supposed to curry belief in some
other theory, which usually has a whole lot less evidence in favor of it than the mainstream belief. There are an infinite number of ways you can run
away from some conclusion, so that's why the typical conspiracy theory ends up being a gaggle of completely unrelated, often conflicting stories. If you take all the JFK assassination theories collectively, there were shooters all over the plaza. There would have been a hail of bullets. A plethora of incompatible "alternate" theories, all trying to explain the same evidence, are just a multiplication of
loose ends.