Lawyers for Saudi Arabian Crown Prince Mohammed bin Salman, facing a US lawsuit over the 2018 killing of Saudi journalist Jamal Khashoggi, told a court on Monday the crown prince’s appointment as prime minister last week ensured him immunity from prosecution. Khashoggi was killed by Saudi agents in the Saudi consulate in Istanbul in an operation which US intelligence believed was ordered by Prince Mohammed, who has been the kingdom’s de facto ruler for several years. The prince denied ordering Khashoggi’s killing, but acknowledged later it took place “under my watch”. Last week his elderly fat…