Donald Trump’s former lawyer and fixer Michael Cohen, is scheduled to testify on Monday, before a Manhattan grand jury investigating hush-money payments made on the former president’s behalf.

Cohen, is a key witness in Manhattan District Attorney Alvin Bragg’s investigation, and his testimony is coming at a critical time, as prosecutors close in on a decision on whether to seek charges against Trump. Prosecutors save their most important witnesses until the end stages of a grand jury investigation.