US authorities are expected to unseal charges against a Libyan they accuse of being the master bomb-maker behind the Lockerbie bombing, only days before the anniversary of the UK’s deadliest terror attack. William Barr, the outgoing US attorney general, is expected to confirm publicly within days that the US has indicted a former Libyan intelligence officer, Mohammed Abouagela Masud, accusing him of completing the device which blew up Pan Am 103 over the Scottish town on 21 December 1988. The bomb killed all 259 people on the flight, mostly Americans returning home for the Christmas holidays. A large section of the plane’s fuselage fell on Lockerbie, destroying homes and killing 11 people on the ground. Barr is expected to stand down next week. His move comes as five of Scotland’s most senior judges are considering a posthumous appeal brought by the family of Abdelbaset al-Megrahi, the only man convicted of the attack. Aamer Anwar, the Megrahi family lawyer, said the decision by the US Department of Justice was designed to sway the Scottish court. “It smacks of extreme desperation that on the eve of a decision on the appeal and the 32nd anniversary of the bombing that they should come up with an indictment of Masud. What have they been doing for the last 32 years? “It’s a weak and tenuous link, trying to connect Megrahi to him,” Anwar said. The latest appeal, the third against Megrahi’s conviction in 2001, was launched after the Scottish Criminal Cases Review Commission referred his case to the appeal court as a suspected miscarriage of justice earlier this year. The three-day appeal hearing chaired by Lord Carloway, the Lord Justice General and Scotland’s most senior judge, ended on 26 November and the ruling is expected soon. Prof Robert Black QC, the lawyer and legal academic who devised the plan to hold the original 2000 Lockerbie trial in a neutral country, the Netherlands, said he doubted the timing of Barr’s decision would affect the Scottish judges weighing up Megrahi’s appeal case. “I honestly don’t think that would have an influence on the Scottish judiciary,” Black said. There had been numerous occasions where contradictory claims had surfaced before with Lockerbie hearings outside the court setting, which had not swayed the court, he said. Masud is named in the original indictment against Megrahi and his then co-accused Al Amin Khalifa Fhimah and accused by the Scottish prosecution of travelling with Megrahi to Malta on the day the bomb was allegedly planted on a feeder flight to Frankfurt, 21 December 1988. Fhimah was acquitted by the court. The charge against Megrahi said he travelled from Tripoli “using a passport in the false name of Ahmed Khalifa Abdusamad, while travelling with said Mohammed Abouagela Masud also a member of the Libyan Intelligence Services”. Barr unveiled the US charges against Megrahi and Fhimah in 1991 while acting attorney general for the George HW Bush administration. It took nearly 10 years of wrangling before the Muammar Gaddafi regime handed the two men over for trial. Despite being named once in the indictment, Masud’s alleged role as a co-conspirator in the Lockerbie attack only surfaced during investigations into the case in 2012 by Ken Dornstein, a journalist working for the US broadcaster PBS, whose brother David was killed in the Lockerbie attack. Dornstein interviewed another Libyan intelligence officer who said Masud was involved in a discotheque bombing in West Berlin in 1986 which killed two US servicemen; that attack had been planned and carried out by Libyan agents. The same source named Masud, by then in jail in Tripoli, as the Lockerbie bomber, Dornstein said. Masud was already under investigation by the FBI and the Crown Office prosecution service in Edinburgh.