Former Haitian leader Jean-Claude "Baby Doc" Duvalier has aplogised to the victims of his brutal 15-year reign.
Mr Duvalier has also called for national reconciliation in his most extensive speech since he returned to the country a week ago after 25 years in exile.
He said he wanted "to express deep sorrow for all those who say they were victims of my government".
He is being sued for torture and other crimes against humanity.
The lawsuit was filed on Wednesday by a former United Nations spokesperson, Michele Montas, and three Haitians who were jailed during Mr Duvalier's 1971-1986 rule.
Ms Montas said she had lodged lawsuits for arbitrary detention, exile, destruction of private property, torture and moral violation of civil and political rights.
It has been estimated that between 20,000 and 30,000 Haitians were killed by the security forces or the paramilitary Tontons Macoutes or "Bogeymen" under Duvalier's father Papa Doc and then under his own rule.
Amnesty International and Human Rights Watch regularly reported on these abuses from the 1960s to the 1980s, and these reports could be used in any future trial.
State prosecutors have also charged Mr Duvalier with theft and misappropriation of funds during his time as president-for-life.
One of his lawyers said he was planning to stay in Haiti despite the charges, and might get involved in politics again.
Speaking in French and Creole at a news conference, Mr Duvalier said he hoped for a rapid resolution to the political crisis in Haiti.
He arrived on the day Haiti was supposed to hold a second round of elections to choose a successor to outgoing President Rene Preval.
That vote has been postponed because of a dispute over which candidates should be on the ballot paper.
Provisional results from the first round on 28 November provoked violent demonstrations when they were announced, and most observers said there was widespread fraud and intimidation.
Handed the presidency at age 19, Mr Duvalier made some attempts to modernise and reform the Haitian state but his rule was arbitrary and authoritarian.
In February 1986 the armed forces toppled him in a bloodless coup supported by the vast majority of Haitians.