Spain's most controversial and famous judge has appeared in court accused of abusing his judicial authority in an investigation into financial corruption.

Investigating magistrate Baltasar Garzón sat in a Madrid chamber on Tuesdaydressed in his court robes at the beginning of a trial that could end his career.

Garzón made his name fighting corruption, international and domestic terrorism and the drugs trade in Spain, and became famous in the UK when he ordered the arrest of Chilean General Pinochet in London in 1998.

He is now facing three separate cases and could be struck off as a magistrate for 17 years if found guilty - bringing his career to an immediate and abrupt conclusion.

Garzón's supporters and human rights activists turned out in force outside the Madrid court ahead of the hearing. They argue that the judge is being persecuted, principally for a decision to investigate human rights abuses committed under the dictatorship of Francisco Franco, for which he was suspended in May 2010.

In the first case, which is being heard in front of a seven judge panel at Spain's Supreme Court in Madrid on Tuesday, Garzón is accused of illegally authorising the police to tap discussions between lawyers and their clients.

Another hearing, which is said by experts to be the more important case, will begin next week and will see Garzón accused of abusing his powers when he opened the investigation of killings committed under Franco.

That case has been brought by a civil servants union, known as Clean Hands, who argue that he ignored an amnesty which was approved by the Spanish parliament in 1977.

"Parliament unanimously approved the amnesty law. Judge Baltasar Garzon takes a stance as if they're crazy. What does he think? That he's better than them," said Miguel Bernard, leader of the union, according to CNN.

A third case, which has not yet been scheduled, is set to test allegations that the judge received payments from Santander for sponsored seminars while on a sabbatical at New York University, before deciding to launch an investigation against the bank.

The university denies the allegations.

Garzón denies all of the allegations and says he will fight them as far as he can.

However it has been reported that he is sure he will be found guilty because of the enemies he has made in the course of his career.