Newey and Patrick Head, Williams technical director at the time, were prosecuted in Italy for manslaughter but eventually acquitted.
The prosecution argued a poorly manufactured modification to the steering column had caused it to fracture and break at the crucial moment.
Williams said all the data pointed to a driver error caused by Senna pushing too hard over bad bumps in a corner made more challenging than normal by the handling problems the car was suffering from at the time.
"There is no doubt it was cracked. Equally, all the data, all the circuit cameras, the on-board camera from Michael Schumacher's car that was following, none of that appears to be consistent with a steering-column failure.
"The car oversteered [when the rear tried to spin] initially and Ayrton caught that and only then did it go straight.
"But the first thing that happened was oversteer, in much the same way as you will sometimes see on a superspeedway in the States - the car will lose the rear, the driver will correct, and then it will go straight and hit the outside wall, which doesn't appear to be consistent with a steering-column failure."
Three-time world champion Senna was killed in his third race for Williams
Newey said he was still upset by the knowledge Senna joined Williams to win a fourth title and the car they gave him was not initially up to the job. He was killed in his third race for the team.
"There was an aura about him, something that's difficult to describe. He most certainly had a presence," Newey said of Senna.
"I guess one of the things that will always haunt me is that he joined Williams because we had managed to build a decent car for the previous three years and he wanted to be in the team he thought built the best car - and unfortunately that '94 car at the start of the season wasn't a good car.
"Ayrton's raw talent and determination... he tried to carry that car and make it do things it really wasn't capable of.
"And it just seems such a shame and so unfair he was in that position. And then, of course, by the time we did get the car sorted, he wasn't with us any longer."
F1's greatest drivers - Number 1: Ayrton Senna
Red Bull's Sebastian Vettel
is poised to pass Senna's mark of three titles this season - the German heads into this weekend's
Korean Grand Prix
with a 60-point lead over his closest rival, Ferrari's Fernando Alonso, with only 150 still available in the remaining six races.
But Newey, 54, said it was "completely unfair" to compare drivers he had worked with in his long career.
Asked if he felt Vettel, still only 26, could match Schumacher's record of seven titles, Newey said: "Yes, of course it would be fantastic if Sebastian could go on to eclipse Michael's record. But that doesn't necessarily define greatness.
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