Frank Williams, the Williams team owner, its technical director, Patrick Head, the Formula One designer Adrian Newey, and three race officials all face manslaughter charges after Senna's fatal crash at the 1994 San Marino Grand Prix.
The trial resumed with the summing-up of the last of the defence cases, put by Oreste Dominioni, who is representing Williams and Head.
The state prosecutor, Maurizio Passarini, recommended earlier this month that Williams and the three race officials be cleared of the charges, but called for one-year suspended jail sentences against Head and Newey.
Dominioni launched a five-hour attack on the prosecution case, claiming that Passarini had been let down by his technical advisers, who had provided him with assumptions and not facts. "His reconstruction of the accident which cost Ayrton Senna his life has no basis in proof, is unfounded and those accused must be cleared," Dominioni told the court.