He representing clients in the areas of aerospace, lighting, as well as many other fields. Prior to entering private practice, he worked in the U.S. Patent and Trademark Office (USPTO) as an Associate Solicitor, handling law suits brought against the USPTO as well as ex parte appeals to the Court of Appeals to the Court of Appeals for the Federal Court. Before that, Marshall served as a USPTO Patent Examiner making patentability decisions regarding inventions relating to illumination technologies.