Mueller has a secret weapon he uses against defendants: Ex-prosecutor
Robert Mueller in 2012 (U.S. Embassy Tallinn)

A former assistant US attorney that worked with special counsel Robert Mueller on a previous case was shocked by how detailed the investigator was — and explained his process in a Tuesday MSNBC interview.

Glenn Kirschner, a former prosecutor for the Army and the District of Columbia, told MSNBC's Nicolle Wallace that he witnessed Mueller "investigate a case in real time" when he worked under the special counsel on a case involving the shooting of a police officer.

"I had been a prosecutor for almost ten years at that point in time, and I thought, 'you know what, I know my way around a criminal investigation,'" Kirschner recalled. "And then I looked in Bob Mueller's investigative boxes, and I was blown away. That's not hyperbole."

"The man was investigating somebody who shot a police officer, and he started with the defendant's birth certificate and he moved forward through the defendant's life," he added. "He knew things about the defendant that I bet the defendant had forgotten about himself."

Given that attention to detail, Kirschner illustrated just how foolish it is to expect that Mueller's story is soon to be over.

"For us to debate whether we have enough to begin impeachment proceedings, whether we might have enough to bring a criminal charge against the president or his family members, is really, it's folly and it's folly that we enjoy," he said.

"This is still the first inning, with respect to this game, and, you know, it may go into extra innings before we know who wins and who loses," Kirschner concluded.

Watch below: