Niles was born and educated in Dallas. Niles attended Good Shephard before going on to graduate from Jesuit College Preparatory School. Niles found his place in academics when he left for college and earned a BA (history), MA (history), and a Ph.D. (nineteenth-century German history) before getting serious and enrolling in law school. Niles graduated from the University of Houston Law Center in the top quarter of his law school class. Niles served as an editor on the Houston Journal of International Law and worked in the law library as an assistant to the reference librarians. Upon graduation, Niles accepted a prestigious and much sought-after clerkship with the Honorable Evelyn V. Keyes of the First Court of Appeals. It was during this clerkship that Niles learned to be an appellate attorney.
Niles takes a very limited number of habeas cases. Generally, these involve claims that a trial or appellate attorney failed to provide constitutionally effective representation. He has also represented clients in election disputes, sales tax contests, and mandamus proceedings.