RIO DE JANEIRO — Brazilians are so used to impunity, especially when it comes to the legendary corruption in their political system, that they often employ a fatalistic maxim to describe it: The police arrest; the courts set free.

But for weeks now, Brazilians have been riveted by the televised spectacle at the nation’s high court, in which justices are sparring over what is arguably Brazil’s largest corruption scandal. When the dust settles and sentences are announced, prominent politicians and bankers may actually go to jail.

The fact the trial is even advancing to such a phase — taking aim at congressmen, members of the governing party and senior officials who worked directly under one of the most popular presidents — points to a rare breakthrough in political accountability and a crucial streak of independence in the legal system.

So far, the court, the Supreme Federal Tribunal, or Supreme Court, has already found more than 20 of the 38 defendants in the case guilty of crimes including money laundering, misuse of public funds and accepting cash for votes.