New York prosecutors trying to convict Donald Trump for falsifying business records face a formidable challenge: They have to convince a jury to trust the word of a convicted perjurer. The credibility of Michal Cohen, Trump’s former lawyer and fixer, dominated the fifth week of the former President’s trial. Cohen’s testimony lies at the heart of the charges that Trump allegedly directed a scheme to hide hush-money payments to porn star Stormy Daniels ahead of the 2016 election and lied on business forms to conceal campaign finance violations.