Argentine public prosecutors have always needed steely nerves to investigate high-ranking officials, business tycoons and criminals, facing blackmail, threats to kidnap their children and attempts to impeach them.

But even to the most hardened, the mysterious death last month of prosecutor Alberto Nisman the night before he was to testify about his allegations that President Cristina Fernandez had tried to derail his probe into a bombing attack came as a shock.

Some say it also laid bare a deep-seated culture of intimidation and meddling in Argentina's courts.