Frank Williams, the owner of the team for which Senna drove at the time of that fateful San Marino Grand Prix, his partner and technical director, Patrick Head, and chief designer, Adrian Newey, as well as three racing officials, are charged with culpable homicide.
The prosecution, armed with a 700-page report, will allege that faulty welding caused the steering column of Senna's car to break, sending him off the track at 192mph and into a concrete wall. Head maintains that the column was intact until impact. All the defendants deny the charges and it is conceivable that we may never know why the 34-year-old Brazilian was killed.
Only 24 hours before Senna's crash, Roland Ratzenberger, a little-known Austrian, died in qualifying. The inquiry decided against pressing charges in his case because of driver error.
Driver error in Senna's case seems unthinkable. Three times world champion, he was regarded by many as the greatest driver of all time. Formula One, as a body, has always contended Senna was simply unlucky, that accidents will happen and usually drivers walk away from accidents such as his.
Except that, in this instance, it is thought, the front, right wheel of the Williams whipped up and smashed into Senna's head, inflicting fatal injuries.
If Williams, the most successful and accomplished team in modern grand prix racing, can be found responsible for an accident, then the rest are patently vulnerable. The threat hangs over the teams, the circuits, the sport's governing body, the FIA, and the future of F1 in Italy.
Hence the united front and the determination that the case should not develop into a Williams versus circuit conflict. Revived suspicions about debris on the track, tyre pressures and the road surface all demand questions of the organisers. One intriguing suggestion is that Senna blacked out after holding his breath for the previous lap.
The other defendants are Federico Bendinelli, managing director of SAGIS, the company that owns the circuit at Imola, Giorgio Poggi, the track director, and Roland Bruynseraede, FIA's race director. Their advocate is an Italian, Roberto Causo, while the Williams officials will be represented by Peter Goodman.
The court, in an administration building in the town, is expected to sit two days a week and the trial is likely to last for about six months. Williams, Head and Newey are scheduled to appear before the judge, Antonio Costanzo, at the end of April. Several leading personalities, including Damon Hill, Michael Schumacher and the sport's marketing chief, Bernie Ecclestone, are due to give evidence.
Hill, who was Senna's team-mate and raced on after the accident, said yesterday: "I could do without it, going through it all again, but under Italian law we have to go through it. If there is anything we can find then we should do so. Lessons have to be learnt.
"Things have changed since Ayrton died, but it will never be totally safe. If Formula One hadn't changed things it would have been remiss.
"Senna's accident highlighted the fact that we have got a responsibility to provide entertainment and not just a macabre spectacle. The safer you make it the better. People can take more liberties and actually improve the show."
There is a belief that all the defendants will be acquitted and a reluctant acceptance that the trial has been staged to satisfy Italian legal procedure.
If Williams and the others are found guilty they could be jailed. In reality, they would be fined or, at worst, given suspended sentences. Appeals would follow and the case could then drag on for a decade. The six on trial are not alone in hoping it does not come to that.Reuse content