John G. Costello

John G. Costello is a Maryland criminal defense and personal injury attorney who represents clients facing charges or seeking recovery after negligence. He handles criminal cases, serious personal injury claims, and related litigation. His background includes work as a prosecutor, judicial law clerk, and private practice attorney. He helps clients understand court procedures, evaluate risks, and prepare for hearings, negotiations, and trials when legal stakes are high for families involved.

Costello earned his B.A. in Communications from the University of Delaware. He earned his J.D. from American University, Washington College of Law. After law school, he clerked for the Honorable Terrence J. McGann of the Montgomery County Circuit Court. That role gave him direct exposure to trial preparation, judicial decision-making, and courtroom procedure in civil and criminal matters.

Costello served for five years as an Assistant State’s Attorney in Montgomery County, where he regularly tried criminal cases before judges and juries. In private practice, he has handled serious personal injury matters for victims of negligence and represented people charged with criminal offenses. He is admitted in Maryland, the District of Columbia, and federal district courts in Maryland and the District of Columbia for litigation matters and injury hearings.

John G. Costello helps people by using trial experience and prosecutor insight to protect rights and pursue recovery. In criminal cases, he reviews evidence, challenges weak claims, and prepares clients for court. In injury matters, he works to show fault, damages, and the impact of harm. His bar leadership and Maryland Bar Foundation fellowship reflect professional respect and a commitment to service within the legal community and profession statewide.

Law Office Affiliations

• Attorney, Alpert Schreyer Criminal Defense Attorneys
• Member, Prince George’s County Bar Association
• Member, Montgomery County Bar Association
• Fellow, Maryland Bar Foundation 2025
• Member, Maryland Association for Justice

Licensed State

• Maryland
• District of Columbia

Education

• American University Washington College of Law
  Juris Doctor (JD)
• University of Delaware
  Bachelor of Arts (BA)

Awards & Badges