19 Questions We Have for Mueller Ahead of His Testimony Before Congress Why didn’t you subpoena the president? The Mueller report says his prosecutors did not want to delay the investigation at a late stage with a subpoena fight that could drag on. They also thought they had “substantial” information from other witnesses that allowed them to assess the president’s actions. Nonetheless, not subpoenaing Mr. Trump was one of Mr. Mueller’s most controversial decisions because it arguably allowed the president to evade hard questions without real political damage.