Glenn Leon returned to the U.S. Department of Justice, after nearly nine years in the private sector, to take over a section that has grown both in staff and in stature as it pursues some of the government’s biggest white-collar cases.

The criminal fraud section in recent years has taken on an outsized importance in the DOJ’s efforts to confront corporate crime, striking high-dollar resolutions with major corporations over violations of the Foreign Corrupt Practices Act and investigating complex schemes involving health care, securities and procurement fraud.