Prosecutors took care to emphasize at the start of former president Donald Trump’s Manhattan criminal trial last month that their credibility-challenged witness Michael Cohen’s testimony would be corroborated by evidence. The message: You don’t have to take his word for it.

But on some key aspects of the case, they’ve still been forced to rely on Cohen’s say-so. That made the cross-examination of Cohen this week the most high-stakes moment of the trial.