Donald Trump‘s former right-hand man is preparing to testify before a grand jury for an investigation that appears likely to produce a criminal indictment for the former president.

Michael Cohen, a longtime friend and attorney for Trump is expected to testify in Manhattan next week about alleged hush money payments he made to adult film actress Stormy Daniels ahead of the 2016 election. The $130,000 payment, while not illegal by itself, might have been linked to Trump’s successful campaign for the White House, prosecutors say.