Thousands of protesters took to the streets of Madrid on Sunday in support of top judge Baltasar Garzon.
Garzon is on trial for abuse of power for probing atrocities during the era of General Franco.
More than 100,000 people died in the Spanish civil war and Franco’s subsequent dictatorship.
Those crimes are covered by a 1977 amnesty law.
Cayo Lara, a politician for the United Left party, said: “We cannot allow for a golden bridge to be built for corruption in Spain and those who want to build a wall of silence around our history.”
Garzon is a darling of Spain’s human rights groups for his willingness to investigate controversial cases.
He shot to fame after indicting former Chilean dictator General Augusto Pinochet.
If found guilty, he could be barred from practising law for 20 years.
Garzon denies the charges against him. The trial continues.