Castell's practice is informed by experience developed while working in the Delaware Department of Justice and clerking in the District of Columbia Superior Court. Prior to joining Venable, he was an associate attorney at a law firm where he represented architects, engineers, and other licensed design professionals. There, in addition to his active litigation caseload, he also counseled clients on stockholders' and operating agreements, stock and asset purchase agreements, bylaws, articles of formation, articles of conversion, founders' agreements, and professional service contracts.
Castell graduated cum laude from the American University Washington College of Law. While in law school, Castell earned several awards for his advocacy skills, including Best Opening Statement during the 2016 Judge Paul Joseph Kelly, Jr. Invitational Trial Competition hosted by Fordham University School of Law and the spring 2017 Highest Grade distinction in Civil Trial Advocacy—an award bestowed by the American University Trial Advocacy Department faculty.