But the Italian, a prosecution witness at the manslaughter trial of six defendants including team owner Frank Williams, did not blame the circuit and said that the Tamburello bend where Senna died was a demanding stretch of track and acknowledged that there must have been an incident.
"A driver like Ayrton Senna wouldn't have left the track at that point unless there was some kind of problem," he said.
Martini said he, Senna and others had noticed a bump in the Tamburello bend before the race which reduced a car's abilities to keep the racing line.
"There was a small bump in the middle that unsettled the cars. I, Senna and others mentioned it 15 days before the grand prix," he told the court.
"The racetrack officials were very efficient, they had it ground down a bit which was the only possible action, but the situation only improved slightly," he added.
However, Martini said that although the cars still grazed the surface with their side-skirts, the drivers just needed to hold the correct line. He said there was only one line into Tamburello and the bump could not be avoided without leaving the track.
Asked whether such a bump could cause a steering column to break, Martini said that he had never known one to do so. He also said that Senna's fast lap time seemed to indicate that his tyres were fully warmed up.
The Italian also told the court that Senna had complained to him three weeks before the race that the handling of his car was "nervous".