It was also the first time for the plaintiffs to see the former ruler known as "Baby Doc" answer direct questions about the widespread abuses associated with his rule.
Activists and opponents applauded as they saw Duvalier arrive for the hearing wearing a navy blue suit and gray tie, and sit facing the three-judge panel. Near him sat his defense attorneys and his longtime partner, who did not remove her sunglasses during the proceedings.
The session was a "historic victory in a country where the rich and powerful have always been above the law," said Reed Brody, counsel and a spokesman for Human Rights Watch. "Who'd have thought that Duvalier would be forced one day to face his victims in a court of law, to submit to questioning about his alleged crimes, and to listen to the names of people who were tortured?"
An attorney for the plaintiffs, Mario Joseph, said the hearing was evidence that Haiti's long dysfunctional justice system "was functioning."
Duvalier had ignored three earlier summonses without consequences but showed up Thursday after a judge warned that he would be jailed if he shunned a fourth.
Several dozen supporters of Duvalier cheered as the former president-for-life shuffled into the courtroom.
The hearing began with arguments over legal proceedings, with Duvalier's defense attorneys initially requesting a closed-door hearing. Lawyers for the plaintiffs asked Duvalier to speak into a microphone but he refused, and the judge accepted.
Instead of speaking to the court, the gaunt-looking Duvalier mumbled his responses to a clerk who sat at his side and recorded them in a ledger book. Then the clerk read the answers aloud in French to the judges.
"I have a positive record and this is in all areas," Duvalier told the court.
The judges also asked him about political prisoners who were locked up, tortured and killed under his regime. They also asked him about a prominent radio journalist who went into exile with his family. And they asked him if he was aware of the murders, executions and political imprisonment that happened during his reign.
"Murders exist in all countries," Duvalier said, who periodically wiped his forehead with a white cloth. In between questions, he looked at the ceiling and rolled his eyes.
Attorneys for the plaintiffs asked Duvalier if he knew of the political prisoners at a notorious prison facility called Fort Dimanche.
"All kinds of delinquents were there," among them drug dealers, Duvalier said.
Robert Duval, a former soccer star who spent 17 months locked up in Fort Dimanche, is among the plaintiffs. During the proceedings, he sat at the edge of his seat and chewed on his nails.
Duval said it was a small triumph that Duvalier was forced to speak before him and others who say they suffered during the dictatorship.
"The whole process has started," Duval said. "We're starting to see his true character."
The steamy courtroom was packed with journalists, activists, Duvalier supporters and representatives from embassies, including the U.S. The crowd, however, remained quiet overall, though the absence of a speaker system made it difficult to hear court discussions.
Thousands were imprisoned, tortured or killed for opposing Duvalier's regime, and he wielded his influence through a private militia known as the Tonton Macoutes. He became president at age 19 after the death of his predecessor and father, "Papa Doc" Duvalier. "Baby Doc" was ousted in 1986 in a popular revolt.
Duvalier made a surprising return to Haiti in early 2011 after spending 25 years in exile. While in exile, Duvalier remained quiet except for a September 2007 radio address in which he apologized for wrongs committed under his rule and urged supporters to rally around his fringe political party.
A lower court judge ruled in January 2012 that Duvalier should only face charges on alleged financial crimes.
The defense and plaintiffs both appealed, setting the stage of these hearings. The defense argues that Duvalier should not face charges of any type, while the plaintiffs are seeking the reinstatement of human rights charges.
The court is scheduled to listen to the plaintiffs next Thursday. Duvalier has not been ordered to attend.