Judge Baltasar Garzon, one of Spain’s most famous crusading judges, is giving evidence at his own trial for ordering a probe into mass killings carried out by Franco’s forces.
He is accused of violating a 1977 amnesty law, which pardonned crimes under the dictatorship to help reconcile the country after 36 years of Franco rule.
Garzon argues that no amnesty exists for crimes against humanity and he wanted to help relatives of the victims recover remains from mass graves.
If found guilty the judge faces a 20-year ban from working as a magistrate in Spain.
Thousands of people have come out in support of Garzon, the man who secured the arrest of Chile’s former dictator Augusto Pinochet in London in 1988.