MURRIETA, Calif. - Four Camp Pendleton-based Marines, including one known as "Psycho," have pleaded not guilty in the execution-style slayings of a fellow Marine and his wife.

Sgt. Jan Pietrzak, 24, and his wife, Quiana Jenkins-Pietrzak, 26, were found gagged, tied and shot in the head in the living room of their Winchester home on Oct. 15. Investigators said the house had been ransacked and a fire had been set, an apparent effort to destroy evidence.