Leonhart also spoke out in support of mandatory minimum sentencing for drug crimes, an issue Holder has highlighted recently as part of his initiative to reduce prison crowding and foster equity in criminal sentencing.

Holder has instructed his 93 U.S. attorneys to use their discretion in charging low-level, nonviolent criminals with offenses that impose severe mandatory sentences.

Leonhart, in response to a question from Sen. Charles E. Grassley (R-Iowa), said: "Having been in law enforcement as an agent for 33 years [and] a Baltimore City police officer before that, I can tell you that for me and for the agents that work at the DEA, mandatory minimums have been very important to our investigations. We depend on those as a way to ensure that the right sentences equate the level of violator we are going after."