Detective Walker (first name unrevealed) is a minor recurring character who first appeared in Penelope.
Nothing is known about Walker, other than the fact that he became a detective and was working in Washington, D.C. by the events of "Penelope".
Walker was part of the security detail for Garcia after she was shot by a serial killer. When the unsub attacks Garcia's apartment and kills a police officer on patrol, Walker is visibly upset about the shooting.
When Jeffrey goes to his high school for safety, Walker helps the BAU in securing the area and, after it is feared the unsub might go on a killing spree, evacuating the school.
- Walker is the first of four police officers to appear more than once in the show's history. The others are:
- Owen Kim, who appeared in the Season One episode Somebody's Watching as a Los Angeles detective, then reappeared in the Season Five episode The Performer as a lieutenant.
- Stan Gordinski, who appeared in the Season Two episode Profiler, Profiled as a Chicago detective, then reappeared in the Season Eight episode Restoration as a Captain.
- Detective Sam Ogilvie, who appeared in the Season Eight episode The Apprenticeship, then reappeared in the Season Twelve episode Taboo.