Testifying in the trial of an American dealer and a former J. Paul Getty Museum curator in Rome, an Italian archaeologist, Daniela Rizzo, said that she had traced dozens of artifacts in top-rate collections — including those of the Getty and the Metropolitan Museum of Art in New York — to Giacomo Medici, an Italian convicted in 2004 of dealing in illicitly excavated antiquities. (He is appealing his conviction.) “I have no doubt whatsoever that these objects come from clandestine digs,” Ms. Rizzo told the court. Defense lawyers countered that Ms. Rizzo’s claims were hypothetical. The American antiquities dealer Robert Hecht and Marion True, the former Getty curator, are charged with conspiring to acquire archaeological treasures looted from Italy. Ms. Rizzo said that other American collectors to whom Mr. Medici sold looted artifacts included Shelby White, a Met trustee; the diamond magnate Maurice Tempelsman; and Barbara Fleischman, a former Getty trustee. Italy has not charged any of them with wrongdoing, but it is negotiating with Ms. White for the return of some pieces.