Prosecutors want to charge Mohammed Ali Malek, a 27-year-old Tunisian, with homicide and people-trafficking.
Mr Malek’s lawyer says his client is keen to tell his story to prove his innocence to the court in Catania.
One of the 28 survivors has given nearly five hours of testimony. Three others are due to speak later.
Prosecutors say survivors identified Mr Malek as the captain of the boat who accidentally rammed the overloaded fishing boat into a merchant ship that had come to rescue it, last Sunday.
The boat capsized with hundreds of migrants allegedly locked in its lower decks and unable to get out.
The death toll is believed to be the highest from a single such incident.
The number of people fleeing war and poverty in the Middle East and Africa has risen sharply in recent months.
More than 35,000 are thought to have crossed from Africa to Europe this year, and some 1,750 have died while attempting the journey.