The Spanish judge known for his investigations of alleged crimes against humanity took the stand Tuesday in his own trial, defiantly rejecting charges that he had overstepped his jurisdiction by probing right-wing atrocities linked to the Spanish civil war.

In a case that has divided Spain like no other, the man credited with promoting the concept that some crimes are so heinous they can be pursued across national borders sat accused by right-wing groups in his native country. Even Spanish prosecutors say he should not have been charged _ but a conviction could end his judicial career.

The judge, Baltasar Garzon, removed his flowing black judge's robe before taking his place Tuesday in the ornate chamber of the Spanish Supreme Court, a stone's throw from another courthouse where Garzon achieved rock star status among rights groups over the past decade.

Both sides in the 1936-39 Spanish civil war _ in which right-wing forces led by Gen. Francisco Franco rose up against a leftist, Republican government and eventually won _ committed atrocities. But the Franco dictatorship carried out a thorough accounting of civilians killed by anti-Franco militia _ and no government agency one has done so for the deaths or disappearances of more than 100,000 civilians at the hands of Franco supporters.

The seven-judge panel overseeing Garzon's trial began the session by announcing it had rejected defense motions to have the case thrown out, on grounds questioning the partiality of the judge who indicted Garzon in 2010.

Garzon declined to take questions from his accusers, which are two right-wing groups. This is a quirk of Spanish law: private citizens can seek to bring criminal charges against someone even if prosecutors disagree.

In Spain, Garzon is highly divisive: while rights groups love him, many conservatives brand Garzon an unabashed publicity hound partial to leftist causes. Many in Spain think Garzon is being punished by fellow judges because of his celebrity status or for reopening old wounds some say are best left be.

At Tuesday's session, Garzon engaged in a carefully orchestrated, legalese-filled back and forth with his defense attorney, Gonzalo Martinez-Fresneda, on the investigation that Garzon began in 2006 and dropped in 2008 in a dispute over jurisdiction.

Garzon said his probe was not about right vs. left on an issue that's still sensitive even though the war ended 70 years ago.

"It is not a question of ideologies," Garzon said. "Here, there were hundreds and hundreds of thousands of victims whose rights have not been addressed."

Garzon recalled myriad dates and resolutions he issued in a sometimes dry exchange that contrasted sharply with the potent drama of the moment: the only judge who dared probe the killing or forced disappearance of what he said were more than 100,000 civilians at the hands of Franco supporters was sitting in court, charged with a crime for doing so and facing the end of his career if convicted.

Garzon reiterated his argument that, under the body of international law that has accumulated since the Spanish civil war, the atrocities could not be covered by an amnesty passed in 1977 as Spain tried to move forward and restore democracy two years after the death of Franco.

He insisted killings and disappearances of civilians at the hands of Franco supporters during and in the years right after the war were systematic and thus a crime against humanity, and that his probe was justified,

"I did what I thought I had to do," Garzon said of his abortive investigation, which ultimately lasted just a month.

He said many of the crimes he probed, such as forced disappearances, were "permanent" ongoing ones because no bodies were found and relatives were thus denied the right to give their loved ones a proper burial.

"Their effects go on in time," Garzon argued, dismissing another plaintiff claim that the crimes were covered by Spain's statute of limitations.

At the time, no Spanish authorities questioned what he had done. It was the right-wing groups' complaint in 2009 that got these proceedings going.

Garzon is perhaps best-known for indicting the late Chilean dictator Augusto Pinochet in 1998, having him arrested while Pinochet visited London in an ultimately failed bid to bring him to Madrid for trial.

Garzon also indicted Osama bin Laden in 2003 over the Sept. 11 attacks in America. Under the doctrine of universal jurisdiction _ the idea that some crimes are so heinous they can be tried anywhere _ Garzon and colleagues at the National Court have gone after rulers and officials from such disparate places as Israel and Rwanda.

Human rights groups have also hailed Garzon for ushering in an era in which victims of systematic crimes such as abuses under former military regimes in Latin America, for instance, were inspired to come forth to demand justice and demand the repeal of amnesty laws.

The judge is facing other legal challenges. He was tried earlier this month for overstepping his jurisdiction by ordering jailhouse wiretaps in a corruption probe. He is also being probed for his ties with a bank that financed seminars he oversaw in New York while on sabbatical in 2005 and 2006.

Tuesday was Garzon's only scheduled day of testimony. The court will now start hearing from people the defense describes as victims of Franco-era crimes, and from human rights experts.

Reed Brody, a lawyer for New York-based Human Rights Watch who was in the courtroom, told reporters that Garzon should not be on trial.

"Garzon showed today that his decision to take up the investigation of the crimes of the Franco era was fully supported by international law," Brody said. "But the spectacle of a judge as a criminal defendant, having to justify his investigation into torture, killings and 'disappearances,' was itself an affront to principles of human rights and judicial independence."