Duvalier has been living in France for the past quarter-century after a popular rebellion drove him into exile. He returned home on Sunday.
Rupert Colville, a spokesman for the U.N. High Commissioner for Human Rights, said Tuesday that it would be easier to bring charges against Duvalier in Haiti because the alleged crimes occurred there.
But he cautioned it is unclear whether Haiti's fragile judicial system is in a position to mount a case.
Duvalier's secret police tortured and murdered political opponents during his rule.