THE appearance of a previously unseen photograph of Ayrton Senna's car at the weekend, showing a piece of debris apparently lying in the path of the Williams FW16 moments before the Brazilian's fatal crash, has failed to impress the Italian magistrate who spent more than two years assembling evidence that will be put before a judicial hearing which opens in lmola today.

"This photograph doesn't change by a millimetre the belief of the examining magistrate that the accident was caused by a fracture of the steering column," Maurizio Passarini, the magistrate, was quoted as saying.

"On the basis of the investigation and the technical findings, he believes that the origin of the accident has been precisely identified. This photograph has no relevance, even if it is reliable. In any case the hearing will have the last word."

Six people have been ordered to appear before a judge to answer charges of culpable homicide - the Italian equivalent of manslaughter - in connection with the crash, which took place on Sunday, May 1st, 1994, on the seventh lap of the San Marino Grand Prix. They are Frank Williams, the founder and managing director of Williams Grand Prix engineering. constructor and entrant of Senna's car; Patrick Head, his partner and technical director; Adrian Newey, their chief designer that season; Federico Bendinelli, representing Sagis, the company that owns the Imola autodrome; Giorgio Poggi, the circuit director; and Roland Bruynseraede, the race director, who sanctioned the use of the circuit on behalf of the FIA, the governing body of world motor sport.

Within the next few months we may find out whether the court considers one, some, all or none of them to have been responsible for Senna's death in an accident which has been the subject of considerable speculation and controversy. Not the least of the factors is the knowledge that Senna went into the race under pressure and in a disturbed state of mind.

When he began the seventh lap that day, the Brazilian knew he was in a race. It was the third round of the world championship. Just behind him was Michael Schumacher, who had won the first two rounds and therefore held a maximum 20 points, at the wheel of a car which, in Senna's mind, might have been exploiting an illegal technical advantage.

The Brazilian had been widely expected to cruise to his fourth title in 1994, his first season with the Williams team, but he came to lmola with nothing - only the disconcerting realisation that the Williams-Renault FW16B was not as good a car as he had expected; not even as good, on the face of it, as Schumacher's Benetton B194.

Senna was in first place, having led off the grid from pole position and maintained his position when an accident on the start-line forced the field to hold station behind the safety car - an Opel saloon driven by an Italian racing driver, Max Angelleli - until the end of the fifth lap.

The sixth lap was run at racing speed, although the drivers were cautious because the effect of the low-speed running had been to cool down their tyres, lowering their pressure along with the temperature - a critical factor in terms of flat-out running, but also vital to safe roadholding at racing speeds since the fat, soft, treadless dry-weather tyres did not produce their maximum cornering grip until they reached something above 80 degrees centigrade.

So at 17 minutes past two o'clock on that Sunday afternoon, Senna led the field past the grandstands and the time keeping tower, and headed out for the long left-hand curve called Tamburello "little drum". His right foot held the pedal to the metal, flat out in sixth gear. He was doing exactly 192 m.p.h when the accident began.

What happened in the next 1.8 seconds - and particularly in the last 1.4 seconds, which were not covered by the video camera mounted alongside Senna's cockpit - has been the subject of almost three years of public speculation and controversy.

The on-board video camera, which captured only the first moments of the incident, showed the car veering away from its normal trajectory in the middle of the curve and heading for the grass strip, 11 yards wide, which separated the track from a concrete perimeter wall.

Passarini set up a panel of half a dozen experts, including a designer, a driver, a doctor and a road engineer, and sent the parts of the broken car out for analysis by scientists at Bologna University and the Italian aerospace laboratory, Pratica Di Mare. Last year he delivered a 700-page report into the hands of an examining magistrate, who concluded that there was a case to answer.