After serving four years as an artillery specialist with secret security clearance through the United States Army, Demetrick Pennie embarked on what would become extensive post-secondary studies at Honolulu Community College in Hawaii. He earned his associate of arts in the administration of justice with honors in 1998 and subsequently found employment with the Dallas Police Department. While working full-time in law enforcement, Demetrick Pennie returned three times to academic environments to secure successive degrees: a bachelor of arts in criminal justice at Midwestern State University in Wichita Falls, Texas; a master of arts in counseling from Prairie View A&M University in Prairie View, Texas; and a doctorate in higher education from Texas Tech University in Lubbock, Texas.

While employed by the Dallas Police Department, Demetrick Pennie held professorships with both Strayer University and the University of Phoenix, teaching classes that included criminal justice and terrorism. In addition to his ongoing work as a Dallas police sergeant, Mr. Pennie serves as the vice president of the Dallas Fraternal Order of Police and a senior administrator with both the Dallas Fallen Officer Foundation and the Texas Fallen Officer Foundation.