(CNN) -- The French investigation into the accident that killed Princess Diana, her companion Dodi Fayed and the driver of their car, Henri Paul, and injured bodyguard Trevor Rees-Jones is not expected to be completed until October.

In the first days after the accident, speculation centered on the horde of photographers pursuing the couple's limousine on August 31, 1997, when it crashed at high speed in the Pont de l'Alma tunnel in Paris.

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It was reported that the limousine was chased by one or more cars and at least one motorbike, and that it may have been sideswiped by yet another vehicle.

But tests revealed that the alcohol in Paul's blood was three times higher than the level at which one is considered to be drunk under French law.

Later tests confirmed that Paul had been in the midst of a bout of "moderate chronic alcoholism for at least a week," and that his blood also contained the antidepressant Prozac and tiapride, a drug used to combat alcoholism.

That he was both drunk and speeding would seem to be enough to pin the blame on Paul. That impression was deepened when it was learned that Paul was not a chauffeur, but the deputy security chief of The Ritz hotel. The hotel is owned by Fayed's father, Mohamed Al Fayed, who also owns Harrods department store in London.

Nevertheless, there have been a number of interesting developments this year as Judge Herve Stephan has conducted his investigation:

February 2: A British tabloid publishes photos of a white Citroen AX that it says might have been involved in the crash. Investigators suspect that the Mercedes driven by Paul might have grazed a white car before crashing but believe it to be a Fiat Uno. They say they have the "most extreme reservations" that the Citroen was involved.
February 12: Al Fayed tells a London paper that he believes the crash "was not an accident" and that the deaths were part of a conspiracy to keep Diana from marrying his son. Al Fayed doesn't say who he thinks is responsible but claims that many in the British "establishment" were happy when Diana and his son died.
February 13: Investigators working for Al Fayed claim to have found the white Fiat involved in the crash. Although the police say they had examined the car before and eliminated it from suspicion, they agree to re-examine it.
March 12: Al Fayed meets with Stephan and, according to one of his attorneys, is "satisfied by everything" the judge tells him. The attorney also says that Al Fayed requested "additional investigations," and wants to know more about the white Fiat theory.
June 5: The judge begins questioning more than 20 witnesses involved in the case, including Diana's mother, Frances Shand Kydd. Al Fayed is among those attending, a day after issuing a statement saying he is "determined to get to the truth" about the accident. "I will not rest until I am satisfied that what happened was God's wish and not the wish of someone else," he says.
Late June: A book published by two reporters from the French magazine L'Express says police have found little evidence that the pursuing photographers caused the accident. But the authors do conclude that the frenzied photographers were more interested in taking pictures of the victims than in helping them. Nine photographers and a press motorcyclist are officially being investigated.
Early July: Rees-Jones asks Stephan to determine whether Paul was competent to drive the night of the accident. He also wants to know whether The Ritz knew Paul was an alcoholic and why Paul was chosen to drive the limousine when he was off-duty and lacked a chauffeur's permit. Speculation has it that Rees-Jones, who quit his job with Al Fayed, may be preparing to sue his former employer for the injuries he suffered in the crash. A friend says Rees-Jones quit his job because he "felt pressured to remember the events in a way in which they might not necessarily have happened."
July 28: A chauffeur who regularly drove the limousine tells Stephan that the car had persistent braking problems and "didn't hold the road well." Olivier Lafaye says one of the owners of Etoile Limousine told him, "Be very careful with this car. Don't brake suddenly or the back end will swing out." Lafaye says Paul didn't know that, and had never driven the car before. "You had to know it well to drive it safely," he says.
August 3: A former French marine tells a British newspaper, "My driving may have caused (the limousine) to swerve and lose control." Francois Levistre, now a truck driver, says he was 10 meters behind the limousine in his gray Ford, and speeding, when the accident occurred. The paper says Levistre was interviewed by French investigators after the crash and at that point had denied any involvement.