David Patterson Dyer completed preparatory studies and attended St. Charles College in Missouri before reading law and being admitted to the bar in Pike County. He spent several years in private practice and served as prosecutor for the Third Judicial Circuit of Missouri. During the American Civil War, Dyer held various military ranks, culminating in his service as lieutenant colonel and colonel in the 49th Missouri Infantry Regiment. He also served in the Missouri House of Representatives and as Secretary of the Missouri Senate. Dyer was elected to the United States House of Representatives and later resumed private practice in St. Louis. He served twice as United States Attorney for the Eastern District of Missouri and was appointed to the United States District Court for the Eastern District of Missouri, where he remained until assuming senior status.

David Patterson Dyer's political career spans a period marked by significant military and judicial service, suggesting a unique blend of legal rigor and wartime experience. His legislative roles during and post-Civil War indicate a strategic focus on stability and regional influence. Dyer's unexpected convergence with opposing factions on certain issues reveals a highly calculated approach, balancing ideological consistency with pragmatic regional interests. His rhetorical style likely emphasizes resilience and experience, drawing on his military and judicial backgrounds to frame policy discussions.