Almost three decades after his grisly killing in Germany the murder of the exiled Iranian entertainer Fereydoun Farrokhzad remains officially unsolved But an investigation by RFERLs Persianlanguage service Radio Farda has uncovered documents that point to Irans intelligence services And a former Iranian spy has revealed a possible suspect in the 1992 slaying of the outspoken critic of Irans hardline Islamic regime