(NBC NEWS) Many of the most popular Kennedy assassination theories have the trappings of a Cold War spy novel: political intrigue, colorful villains and labyrinthine twists and turns.
But at least one theory that has gained traction in recent years has a relatively straightforward storyline: The assassination of President John F. Kennedy was a tragic accident — not the work of a sinister gunman or a conspiracy to topple the king of Camelot.
There are no Mafia dons or Soviet pawns at the center of the so-called "accident theory" — just an ordinary Secret Service agent with a bad case of butterfingers.