President Donald Trump says he can fire Special Counsel Robert Mueller. However, constitutional expert Robert McWhirter argued on Arizona Horizon that President Trump probably can’t fire Mueller unless he's done something wrong.

He said Mueller also took steps to protect his investigation into Russian interference in the 2016 election.

"Robert Mueller did something very interesting," McWhirter said. "He made it a joint investigation with the attorney general of New York, which means that even if Donald Trump fires Robert Mueller this investigation goes forward.”

McWhirter said the only historical precedent happened in 1973, when President Richard Nixon fired special prosecutor Archibald Cox. However, Cox’s firing didn’t mean the end of the investigation into the Watergate scandal.