PARIS (AP) _ A simple, tragic car accident, caused by a drunk driver. Is that the whole answer?

That's what Judge Herve Stephan will try to find out today when the key witnesses in the Princess Diana case, the photographers under investigation, their lawyers, and Mohamed Al Fayed converge on Paris' main courthouse.

Stephan has summoned the parties for a closed-door hearing to try to clarify the main question in the case: Who was at fault?

The crash in a Paris traffic tunnel Aug. 31 killed Diana, her boyfriend Dodi Fayed, and driver Henri Paul. Tests showed Paul was drunk at the time.

But what was the responsibility of the paparazzi trailing Diana's Mercedes that night?

Nine photographers and a press motorcyclist have been placed under formal investigation _ one step short of being charged _ for both manslaughter and failing to come to the aid of a person in danger.

Those close to the case believe the photographers will soon be exonerated _ at least on the manslaughter charge.

Al Fayed, the father of Dodi Fayed, plans to attend. He has filed as a civil party in the case, and therefore has access to documents and proceedings.

It isn't just his son's death that connects Al Fayed to the case. Driver Paul was an employee of the Ritz Hotel, which Al Fayed owns.

In a statement issued by his spokesman in London, Al Fayed said Thursday he is ``determined to get to the truth'' about whether the crash was an accident or a plot to kill Diana and his son.

``I will not rest until I am satisfied that what happened was God's wish and not the wish of someone else,'' he said, according to spokesman Lawrie Meyer.

But French judicial sources said recently that Al Fayed has backed off his contention that the crash stemmed from a plot, and now thinks the paparazzi are to blame.

Although the probe is not complete, investigators have long believed it was Paul's drunken condition and the Mercedes' excessive speed that probably caused the crash.

They also are still looking for a white Fiat Uno believed to have brushed the Mercedes before it crashed. But they are said to have long given up any real hope of finding the Fiat.

Tests are still being conducted on the wrecked Mercedes that Diana was traveling in, but aren't likely to be finished before October _ meaning the case can't be closed until then.

Investigators also recently conducted road tests on a race track near Paris to reconstruct the crash. Police revealed no details of those tests.

One person who wasn't planning to attend today's session: bodyguard Trevor Rees-Jones, the sole survivor of the crash. He was invited on an ``informational basis,'' but decided not to come.