John William Keker Jr. is a prominent American trial lawyer and defense attorney specializing in criminal defense, complex litigation, white-collar criminal defense, intellectual property, and antitrust litigation. Born in 1944 in Peru, Indiana, he grew up in a Midwestern family and developed an early interest in law and public service. He attended Princeton University, graduating with a Bachelor of Arts degree in 1967, then served in the United States Marine Corps during the Vietnam War as an infantry officer, earning the Silver Star for gallantry and the Purple Heart for combat wounds. After military service, he earned his Juris Doctor from UC Berkeley's Boalt Hall School of Law in 1972.

Keker began his legal career as an assistant U.S. Attorney in the Northern District of California before transitioning to defense work. He gained national prominence in the 1980s as lead defense attorney for Lt. Col. Oliver North during the Iran-Contra affair trials. Over subsequent decades, he has represented high-profile clients in landmark cases including Wall Street executive Frank Quattrone, cyclist Lance Armstrong in doping-related matters, and tech entrepreneur Elizabeth Holmes in the Theranos fraud case. He co-founded the firm Keker, Van Nest & Peters LLP (also known as Keker & Van Nest LLP) in 1976 with partner Elliot Peters, based in San Francisco.

Throughout his career, Keker has been recognized for his aggressive courtroom style and commitment to civil liberties, often taking on cases that challenge government overreach. He has taught trial advocacy at Stanford Law School and received numerous accolades including being named one of the '100 Best Lawyers in California.' As of recent years, he continues to practice law actively, maintaining a reputation as one of the nation's top defense attorneys.