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John Costello

  • Profile
  • Credentials

John Costello’s practice focuses on the representation of victims of personal injury due to the negligence of others.

John is a native of Silver Spring, Maryland. He attended the University of Delaware where he received a Bachelor of Arts in Communications. Later on, he received his J.D. from American University Washington College of Law.

He became interested in the legal field early on in his life due to his father and grandfather both being attorneys. He has always been passionate about helping others who are in need, so naturally, he was drawn towards this line of work.

After completing law school, John began his law career as a clerk for the Honorable Terrence J. McGann of the Circuit Court for Montgomery County. Upon completion of his clerkship, he then spent the next five years as an Assistant State’s Attorney with the Montgomery County State’s Attorney Office. During this time, he prosecuted criminal matters on behalf of the State of Maryland, gaining invaluable court experience trying serious criminal cases before judges and juries on a regular basis.

Most recently, he worked at a litigation firm in Prince George’s County with a primary focus on personal injury and criminal defense. Years of prosecuting criminal cases afforded him a unique and advantageous perspective in defending individuals charged with crimes. Additionally, he successfully handled personal injury matters on behalf of both plaintiffs and defendants. It was during this time that he developed a desire to advocate on behalf of personal injury victims exclusively.

He is a member of the Maryland Association for Justice, the Montgomery County Bar Association, Prince George’s County Bar Association, Maryland State Bar Association, and District of Columbia Bar Association.

During his free time, John enjoys being active, watching and playing sports, and spending time with his wife. He enjoys rooting for Washington sports teams, particularly the Washington Football Team.

Bar Admissions

Washington, D.C.


American University Washington College of Law, Juris Doctor, J.D.
University of Delaware, B.A. in Communications 


  • Maryland Association for Justice (2021)
  • District of Columbia Bar Association (2019-Present)
  • Prince George’s County Bar Association (2016-Present)
  • Maryland State Bar Association (2016-Present)
  • Montgomery County Bar Association (2011-Present)

Words About The Firm

Clients Share Their Stories
    Andrew was so patient with my many questions

    ““My husband and I dealt with Andrew Burnett. I could not have been happier. Andrew was so patient with my many questions. He explained everything that I should expect to happen and he was correct. He ...”

    - Linda Giannini Wilson
    Suzanne is awesome and super personable!

    “The entire team I worked with was amazing. Everyone was welcoming and made sure I was clear on what was going on step by step. Suzanne is awesome and super personable.”

    - Tracy McLean
    Debbie is a straight shooter

    “Potter Burnett is an outstanding firm. I recommend to anyone from any walk of life. Debbie is a straight shooter who fights vigorously for her clients.”

    - Carey Nelson
    I was always informed of where we were with the process

    “Just wanted to take a moment and share with everyone how happy I was with my experience with Debbie Potter and her cracker jack team. I was always informed of where we were with the process and ...”

    - Bob Dyer
    Great people!

    “They were so helpful and consistent with my case great people who really cares about you! I absolutely would do business with them again.”

    - Ceona Monae


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