The pattern we're now so familiar with — news event, faulty early reports, conflicting eyewitnesses, the inevitable conspiracy theory — began with the assassination of President Kennedy. There were conspiracies before he was killed, of course, but that mix of shock and mass media served as both roadmap and justification for conspiracy theories to follow.

On Friday morning, MSNBC's Morning Joe ran a feature on the 50th anniversary of the assassination, asking, at one point, if we could "ever know the truth" of what happened that day. In one sense, the answer is an obvious no — the tiny details of when and how and why anything happens are generally unknowable. In another sense, the answer is yes, we do. Kennedy was shot in the head by Lee Harvey Oswald. But there are enough tiny details that emerged in 1963 and subsequently that anyone who wants to doubt that truth has ample evidence at which he can point.

From the first moments of coverage that day, the news media got details wrong. At right, NBC's report. In its first few seconds, the following inaccuracies are relayed, albeit with caveats: two shots were fired, it was possibly an automatic weapon, there may have been multiple assailants. Within two minutes, listeners are assured that the president is still alive — though he was already dead. A man and a woman were seen "scrambling" across the bridge over the triple underpass near the assassination site, though any connection to the shooting isn't known.

All of this, fodder for future conspiracy theories. Was there a shooter on the bridge, or, perhaps, on the grassy knoll at the right front of Kennedy's car? In the ABC News clip at left, a young family describes the shooting. They were standing on the knoll, and the father repeatedly indicates that the shots came from behind them. The knoll quickly became a focus of theories; a low resolution photograph has been scrutinized for decades for evidence of a shooter in that location, with eagle-eyed theorists picking out a man in a police uniform taking aim at the moment the shots were fired. A British conspiracy site lists nearly 40 other people who also believed the shots came from that location, emphasizing eyewitnesses despite the known flaws in such evidence.

We see this pattern in subsequent events. In the aftermath of the September 11th attacks, theorists scoured news images and video for clues to support their theories of what happened. Here, for example, a page using selective news clips and eyewitness reports to argue that the World Trade Center fell as a result of implosion. After Sandy Hook, someone created this widely-viewed video, using news reports offering conflicting details about multiple shooters and the details of the event to cast doubt on the so-called "official" story. During the Boston bombing in April, there was "roof man," a photo taken by en eyewitness that captured both the second blast and a silhouette on a nearby rooftop. In 1963, it was a man and a woman on a bridge. In 2013, it's a guy on a roof.

Social media has exacerbated the problem of picking out details to support a conspiracy theory, as roof man shows. But that, too, began in Dallas. The Zapruder film, the definitive, familiar color footage of Kennedy's death, spawned its own set of theories once the public got access to it 12 years after the event. "Back and to the left," the mantra burned into the public imagination from Oliver Stone's JFK, refers to the motion of Kennedy's head after the fatal wound. Closer examination shows that the moment the bullet hit, his head went forward. But that detail wouldn't have fit neatly into Stone's narrative — or that of other theorists.

As the news media rushes to cover a story, it makes mistakes — from the Titanic to the D.C. Naval Yard. When those mistakes are corrected, there are two responses. You can accept that an error was made or you can see the correction as an attempt to obscure reality, to hide the truth. The latter choice often reinforces existing beliefs — of a government seeking to confiscate guns (as in Sandy Hook or Boston), or of a government looking for an excuse for war (as after 9/11).

When America's young president was murdered in Texas after months spent battling Cuba and the Mob, it was understandably hard to think that it was the work of one, unfortunately lucky shooter. As the country and a federal investigation grappled with the dichotomy between the importance of the act and the unimportance of the actor, a new American obsession was born. The blame for the conspiracy theory doesn't lie in conflicting evidence, it lies in the faulty human tendency to rationalize the irrational, a sort of conspiratorial pareidolia. Kennedy's killing established the pattern that gave us the Reddit manhunt and Sandy Hook conspiracies. So far, nothing's offered us an antidote.