FBI Director James Comey is testifying this morning before the House Oversight Committee on the decision not to charge Hillary Clinton for her use of a private email server while she was secretary of state.

Comey said Tuesday Clinton was "extremely careless" with classified information, but recommended that the Justice Department not pursue criminal charges.

Over the past 48 hours, critics, including Rudy Giuliani, have argued that Clinton should have been charged for displaying "gross negligence" with classified materials. 

He said that in his mind, there is no difference in the two terms.

Rep. John Duncan (R-TN), a former judge, pressed Comey for the legal difference being "extremely careless" and being grossly negligent. 

Comey answered that there isn't a great definition of "gross negligence" in the law and courts interpret it differently. 

He added that some courts interpret it as a defendant knowingly doing something wrong. Comey said he used the term "extremely careless" as a "common sense" way of describing the situation.

"The question of whether that amounts to gross negligence, frankly, is really not at the center of this," said Comey. 

He said that there was only one case brought on a "gross negligence theory" in the past 100 years.

"Where were these cases? They just have not been brought. ... It's a good thing that the Department of Justice worries about prosecuting people for being careless. I don't like it. As a citizen, I want people to show they knew they were breaking the law and then we'll put you in jail," said Comey.

He later added that he believes it could be established that Clinton was negligent, but not that she acted with "the necessary criminal intent."

Watch the exchange above.