Federal prosecutors have chosen not to open a criminal case into how the late actor Heath Ledger was able to get the painkillers that contributed to his death earlier this year. Lately, prosecutors in the U.S. attorney’s office in Manhattan had been overseeing a Drug Enforcement Administration probe into whether the painkillers found in Ledger’s body were obtained illegally. Prosecutors decided not to open a case because they don’t believe that there is anybody to make responsible for his death. The actress Mary-Kate Olsen was Ledger’s close friend and played a part in this decision because she demanded immunity before answering questions about his death and drug use. A case can still be opened if there is evidence of a crime.

DEA investigators suspect that the painkillers found in Ledger’s body were obtained with false prescriptions and illegally in other ways. The painkillers oxycodone and hydrocodone were found in his system. Ledger had also taken anti-anxiety mediation and sleeping pills that were legally prescribed by doctors in California and Texas.