Tomorrow marks the 55th anniversary of the assassination of John F. Kennedy, the 35th president of the United States.

On 22 November 1963, Kennedy and his wife Jackie drove through Dallas, Texas, in an open-topped car, before he was shot and killed.

The murder of the popular Democratic leader “permanently transformed American politics”, CNN says, “thrusting the nation toward a long overdue - and still unfinished - reckoning with our democracy’s painful history of violence and racism”.

The official account states that former US Marine Lee Harvey Oswald shot and killed Kennedy from the nearby Texas School Book Depository building. But ever since the murder, conspiracy theories ranging from the mad to the plausible have circulated, thanks in no small part to the subsequent murder of Oswald himself in the immediate aftermath of the crime.

Here are some of the most notable examples:

The “official” version

In 1964, the Warren Commission concluded Kennedy was killed by a lone assassin – Lee Harvey Oswald – while three other investigations, in 1968, 1975, and 1978-79, confirmed the commission’s conclusion that JFK had been killed by two shots from behind.

However, the 1978-79 House select committee on assassinations decided there was a high probability that a second gunman fired at Kennedy and that he was “probably assassinated as a conspiracy”.

This finding was itself rejected five years ago by a team of historians and retired secret service officers, who used the latest digital technology to analyse all available film of the shooting and offered a “categorical confirmation” that Oswald acted alone.

But the competing conclusions of the FBI investigations and government commissions have encouraged many to reject the official version.

The ‘magic bullet’ theory

Oswald fired just three bullets in Dallas. But he killed JFK and badly wounded Governor John Connally who was sitting in front of the president. The Warren Commission - the investigation into JFK’s killing set up in 1963 - came up with the “single-bullet theory” to explain how Oswald did so much damage with just three rounds.

It posits that both men were hit by a single bullet which “entered JFK’s upper back, exited his throat, and then struck Connally, breaking a rib and shattering his wrist, and finally coming to rest in his thigh,” says the Mary Ferrell Foundation. Sceptics say the trajectory was fanciful and re-named it the “magic bullet theory”. It’s just one reason why conspiracy theorists think more than one shooter was involved.

The grassy knoll

Most JFK conspiracy theories pivot around the idea that Oswald wasn’t acting alone. When the president was hit by the bullet that killed him, the motorcade was passing a grassy knoll on the north side of Elm Street. Newspaper photographs record that shortly after the shooting, police arrested three tramps found in a railroad car behind the knoll. Because the men were clean-shaven and well dressed there was speculation that they were CIA assassins rather than hobos.

Rafael Cruz

During his presidential campaign Donald Trump insinuated that Senator Ted Cruz’s father was connected to the assassination. His comments were based on a photo published by the National Inquirer, which the tabloid claims shows Rafael Cruz distributing leaflets with Oswald just months before he murdered the president.

Trump seized on the story to attack his then-rival, saying: “I mean, what was he doing – what was he doing with Oswald shortly before the death? Before the shooting?” The story, and Trump’s comments, were quickly rubbished by Cruz and the press. “Now let’s be clear: This is nuts. This is not a reasonable position. This is just kooky,” Cruz told USA Today. “I guess I should go ahead and admit yes my dad killed JFK, he is secretly Elvis, and Jimmy Hoffa is buried in his backyard."

The long list of culprits

If Oswald was a paid assassin rather than a disaffected loner, who was writing his pay cheques? The list of candidates is long, but some names are put forward more than most. They are:

The CIA: The idea that the assassination was a CIA plot sounds bizarre, but conspiracy theorists suggest the president’s alleged comment that he wanted to “splinter the CIA into a thousand pieces and scatter it to the winds” made him an agency target. Other theories suggest that one of the tramps (see above) was E Howard Hunt, a former CIA operative who was involved in the ill-fated Bay of Pigs operation to oust Cuban leader Fidel Castro.

For JFK expert, Dave Perry, this is the most interesting theory. “The problem is, of all of them, this is one I can't debunk,” he told CNN.

Perry points out that a former head of the CIA, Allen Dulles, was a member of the Warren Commission, the special Johnson-appointed panel in charge of the official investigation of the assassination. The commission determined that Oswald acted alone.

The Mafia: Why would the mafia want JFK dead? Because his brother, Robert, was turning up the heat on organised crime. Robert was the US attorney general at the time and his “anti-mafia crusade” had led to a sharp increase in the number of prosecutions of senior mafia figures.

The KGB: “The Soviets had a palpable, powerful motive [to kill JFK]: to gain revenge for the humiliation of the USSR in the 1962 Cuban missile crisis,” says Scientia Press. Oswald was a communist and had spent time in the USSR. His “Russian odyssey” afforded the KGB “many opportunities to interact with him”.

Lyndon B Johnson: In 2003, a Gallup poll revealed that 20% of Americans believed Johnson had something to do with JFK’s death. Theories include the vice president’s “desire to become president, his need to cover up scandals, and his involvement with the FBI", says the Environmental Graffiti website.

This is based primarily on statements made by Madeleine Brown, who alleged to have had an affair with Johnson but who Perry describes as a “crackpot”. Brown long claimed she attended a party the night before the assassination with ex-Vice President Richard Nixon and FBI Director J. Edgar Hoover in which LBJ whispered into her ear, “After tomorrow, those Kennedys will never embarrass me again. That's no threat. That's a promise.”

Not only does Perry say this LBJ could not have been at the party, he also suggests a possible source for the origins of the rumours he was behind the attack.

“A lot of Texans didn't like Johnson - they thought he was a crook - so as a result, they started creating this fiction after the assassination where he wanted Kennedy out so he could be president,” Perry said.

The Little Green Men: Another theory suggests JFK was killed for showing too much interest in “alien activity”. There are two “crucial” pieces of evidence backing this up. The first is a letter written by JFK to the CIA in which he demands to see secret UFO files. The second is a note from a senior CIA official that says “we cannot allow” the president to see the classified material.

The Illuminati: The secretive powerbrokers who control the world are obvious candidates for a JFK conspiracy theory. The president fell foul of the Illuminati, it has been suggested, because he wanted to end the Vietnam War, a conflict that was paying the “shadowy bankers” handsome dividends. The Illuminati were also “angered” by JFK’s attempts to “rein in” the power of the US Federal Reserve, triggering a deadly backlash.

The military industrial complex: The theory that the so-called military industrial complex, a phrase coined by President Dwight Eisenhower to describe the informal alliance between a nation’s military and its arms industry, was behind the assassination has gained traction over time.

Conspiracy theorists point to Kennedy’s intention to pull US troops out of Vietnam, a decision later reversed under President Johnson, as the motive the army (and those looking to profit from the war) had to get rid of him.

Jackie Kennedy: One of the more far-fetched theories alleges that JFK’s wife killed him herself. Could the president’s wife have been a secret assassin? Some theorists claim that Jackie Kennedy hid a pistol in a nearby flowerpot after the assassination. But, as the Daily Mirror notes, “many of those who make the claim seem to overlook the fact that she was being watched in an open limousine by thousands of onlookers”.

The man with the black umbrella: Some witnesses point to a “mysterious” man holding an umbrella as JFK’s motorcade drove by. The day of the assassination was bright and clear; no one in the crowd is wearing a raincoat or carrying an umbrella except one man. And that man is standing right where the shots were fired.

Investigator Josiah Thompson says: “The only person under any umbrella in all of Dallas [is] standing right where the shots come into the limousine. Can anyone come up with a non-sinister explanation for this?"

When challenged to explain himself, the man carrying the umbrella, Louie Steven Witt, testified before the house select committee on assassinations that the umbrella was a protest against the appeasement policies of JFK’s father. The umbrella was a reference to the trademark accessory of Neville Chamberlain, nicknamed the Umbrella Man, who prior to the Second World War had advocated making concessions to the Nazis to try to avoid conflict. Many accepted Witt’s explanation.

The driver: Proponents of this theory suggest secret service agent William Greer, the driver of JFK’s limousine, pulled the trigger. But others, including JFK Lancer, say that what initially looks like a handgun when seen at speed is simply the reflection of the sun on the hair of Greer’s colleague Roy Kellerman.

Friendly fire: Not all sceptics rely on elaborate conspiracies to explain the killing. A simpler alternative suggests that one of JFK’s own bodyguards fired the fatal shot by accident. As Oswald fired on the president, the theory goes, Secret Service agent George Hickey cocked his automatic rifle to return fire. When the car he was in stopped suddenly, he discharged his weapon by mistake. “It’s not sexy. It’s not rife with intrigue,” Bonar Menninger, a journalist and proponent of the theory, told NBC News. “But for that reason, in my mind, it’s extremely compelling - because it’s the only theory that hews tightly to the available evidence.” Hickey sued for libel in 1995, but a judge ruled that the statute of limitations had passed and dismissed the case.

What have declassified documents revealed?

In April 2018, the National Archive released previously withheld documents in accordance with the JFK Assassination Records Collection Act (1992). Although most of the documents (88%) have been accessible by the public since the late 1990s, many have been intrigued as to what details the remainder might entail.

The papers marked “for the president’s eyes only” revealed how Oswald planned to escape, confirming rumours that he visited the Cuban and former Soviet Union embassies in Mexico City in September that year.

Some evidence that redactions or w/holding on #JFKfiles in part due to concern re harm to "foreign relations" 1975 memo from a researcher lists "mexican police" surveillance camera at USSR Mexico City embassy. Today's release redacts what has been public https://t.co/TbCAZM7AAE pic.twitter.com/qIiN3ARrAR — Gerald Posner (@geraldposner) April 26, 2018

Intelligence chiefs believe this was to arrange for visas so that he could travel to the USSR via Havana. “But conspiracy theorists looking for CIA plots are likely to be disappointed as many of the intelligence briefs remain partially blacked out,” Sky News points out.

One historian who has been researching the trove of declassified documents hopes to put some of the wild theories about JFK’s assassination to rest.

“I’ve gone through each of the conspiracies one by one, trying to line them up, and could just never make [them] jump,” Timothy Naftali told The Guardian. “I believe it was Lee Harvey Oswald [who killed Kennedy].”

The Cambridge connection

One of the more bizarre revelations to come out of the latest classified file release was reports that a British local newspaper, the Cambridge News, received an anonymous call about “some big news” in the US, shortly before JFK was assassinated.

According to a declassified CIA memo the call was made to a senior reporter at the newspaper at 18:05 GMT on 22 November 1963, 25 minutes before the first shot was fired.

Reported by MI5 and passed on to the CIA, the memo read: “The caller said only that the Cambridge News reporter should call the American Embassy in London for some big news and then hung up.”

“The Cambridge reporter had never received a call of this kind before, and MI5 state that he is known to them as a sound and loyal person with no security record.”

In a video posted on the newspaper’s website shortly after the memo was made public, the paper’s current chief reporter Chris Elliott, said “no one has ever been able to establish whether that call was actually made” but the fact that it might have been made came to light in the 1980s after a document was discovered allegedly from the CIA reporting the incident.

The Zapruder film

If there is one piece of evidence that has served to both dampen and fuel Kennedy conspiracy theories more than any other it is the 26-second Zapruder film.

Recorded with an eight-millimetre camera by Dallas dressmaker and amateur filmmaker, Abraham Zapruder, it documents the shooting of the president from beginning to end just 486 frames.

Video of Zapruder Film Slow Motion (HIGHER QUALITY)

It has been described as the most important 26 seconds of film ever recorded and has become “one of the great cultural icons of our time” says The Guardian, loved by Andy Warhol and conspiracists alike.

But while the film, which is actually in two parts, is instantly recognisable, its history is also the subject of intense controversy. Shown to the FBI and Secret Service shortly after the assassination, Zapruder was left with the original copy which he entrusted to Life magazine out of respect for the Kennedy family.

Although the magazine published split-second stills from the film in a special issue a week after shooting the full film was kept underwraps from the public for the next 12 years until a bootleg copy was aired by TV host Gerlado Rivera in 1975.

“Keeping it from the public fuelled conspiracy theories that the government had something to hide” says CBS News.

Yet despite being one of the most analysed, watched and talked about films of all time, Zapruder, who died in 1970, never profited from it himself. Finally in 1999, the government agreed to pay the Zapruder family $16 million to preserve the film in the National Archives.

Could JFK have survived?

For all the competing conspiracy theories, there is a remarkable acceptance of one point: President Kennedy did die on 22 November 1963. “Not even the crankiest crank argues that JFK is hiding out in a Boca pad with Jimmy Hoffa and DB Cooper,” says Vanity Fair.

But on this point too there is room for disagreement on the details. Some believe that the president was still alive when he arrived at Parkland Hospital; others that he was dead before the final shot had been fired. Establishing the precise moment of his death is difficult, not only because of the chaos in the aftermath of the shooting, but also because there is no clear-cut definition of life and death in cases such as JFK’s.

“The time [of death] was fixed at 1pm, as an approximation,” the Warren Commission stated, “since it was impossible to determine the precise moment when life left the President.”

The report suggested that JFK could have survived the neck wound caused by the first shot, but not the brain damage that resulted from the second. “From a medical viewpoint, President Kennedy was alive when he arrived at Parkland Hospital,” it said. “The doctors observed that he had a heart beat and was making some respiratory efforts. But his condition was hopeless, and the extraordinary efforts of the doctors to save him could not help but to have been unavailing.”

But the discovery of the President Kennedy film logbook has lent credence to the idea that JFK may have survived.

Handed over to Gizmodo’s Matt Novak and painstakingly produced by White House projectionist Paul Fischer, the logbook details every single film shown in the White House as well as the names and details of those who attended.

According to the logbook, “a film was screened at the White House on November 29, 1963 for twenty people,” says Novak.

Fischer wrote it down as “Little John Birthday Party,” “presumably referring to John F. Kennedy Jr., born on November 25, 1960,” he adds.

But incredibly both President Kennedy and the First Lady are listed as being in attendance at the screening, which took place a week after the President’s death.

“We might be able to chalk it up as Fischer being exhausted and confused or maybe it was written in advance,” says Novak. But the meticulous nature of Fischer’s record keeping seems to suggest that would be unlikely.

“Did JFK somehow survive and live out his life under an assumed name in Cuba?” asks Novak.

“That seems unlikely, given the autopsy photos. But it probably wouldn’t be the weirdest conspiracy theory out there.”

What happened to Lee Harvey Oswald?

Less than an hour after Kennedy was assassinated, a police officer named JD Tippit stopped Oswald, who shot him at point blank range. Oswald, a 24-year-old former marine who had defected to the Soviet Union and returned to the US with a Russian wife the previous year, was later apprehended at a nearby cinema.

Two days later, when he was being transported from police headquarters to a more secure county jail, Oswald himself was shot. Jack Ruby, a nightclub owner, emerged from a crowd of police and reporters, who had gathered to see Oswald taken away, and fired a pistol into his stomach. Oswald was taken to Parkland Hospital and died just ten feet away from the room where Kennedy had died two days before.

Some believe Oswald was killed in order to stop him from revealing a larger conspiracy theory. Ruby claimed he was so outraged by the president’s death that he had suffered “psychomotor epilepsy” and shot Oswald unconsciously. However, he was found guilty of murder with malice. Although he was initially sentenced to die, a court of appeal later ordered a retrial and he died of lung cancer in 1967 before it could be held.