Dennis was born in Poplarville, Mississippi on April 28, 1949. His parents were Arthur and Mary Hazel Smith. Arthur lived from January 12, 1920 to November 6, 1991, and his wife, Mary Hazel, lived from December 3, 1923 to May 14, 2012. Dennis was their only child. Dennis's religious preference was Protestant, but he had no denomination.
When Dennis graduated from high school, he went to a trade school and studied electronics. His last known address was from Columbus, Mississippi, but there is nothing tying him to Columbus at the time of his graduation.
Dennis was not drafted, rather he signed up for the United States Marine Corps. He was unmarried when he went to join in Jackson, Mississippi.