The fourth week of witness testimony in Donald Trump’s hush money trial could be a doozy: Michael Cohen, the prosecution’s star witness, has taken the stand. The long-anticipated testimony on Monday from Trump’s former lawyer and personal fixer follows a breathtaking buildup by prosecutors of a case that ultimately hinges on record-keeping. Trump is accused of falsifying internal business records to cover up hush money payments that Cohen made as part of efforts to buy and bury stories that might hurt the former president’s 2016 campaign.