John has tried cases in federal district courts from New York to California and state courts from Maryland to New Mexico. He has argued appeals in the United States Supreme Court, nine federal circuits, and the appellate courts of several states. John has served as co-counsel for the defense in some of the most notable cases of the past three decades, including United States v. Oliver L. North, United States v. Wen Ho Lee, and United States v. I. Lewis "Scooter" Libby.
In addition to conducting trials and appeals nationwide, John represents witnesses, subjects, and targets in grand jury proceedings and other investigations. He handles habeas corpus proceedings in federal and state courts. He writes amicus curiae briefs for the National Association of Criminal Defense Lawyers in the United States Supreme Court and the federal courts of appeals. And he writes and speaks widely on criminal law issues.