Sean O'Brien | Chicago Criminal Defense Lawyer

Sean’s career is characterized by his dedication to legal excellence, his strategic acumen in criminal defense, and his commitment and loyalty to both his clients and his community.

Sean O’Brien is an accomplished attorney with a robust background in criminal defense and extensive trial experience. His strategic approach involves an aggressive and meticulous analysis of discovery, thorough legal research, and the development of comprehensive strategies to mitigate client risks and secure favorable outcomes. Sean is adept at negotiating with prosecutors and leveraging his reputation and extensive courtroom experience to highlight weaknesses in prosecutions, often achieving beneficial settlements. He also focuses on 4th Amendment litigation, where he has developed a reputation for his aggressive motion practice and consistent litigation success, achieving acquittals in cases ranging from large drug cases, weapons charges, to attempt murder.

Prior to going into private practice, Sean served as an Assistant State’s Attorney for the Cook County State’s Attorney’s Office. In addition to his practical legal experience, Sean has contributed to legal education as a Trial Advocacy Professor and Trial Team Coach at The John Marshall Law School. Sean has taught courses in trial advocacy and evidence and coached several trial teams to success in competitive rounds. His academic contributions demonstrate his commitment to fostering the next generation of legal professionals.

Sean holds a Juris Doctor from The John Marshall Law School, where he graduated with honors.  He was actively involved in the Trial Advocacy and Dispute Resolution Honors Board, serving as Vice Barrister and Chief Barrister. He was also selected as class representative for the Chicago Inn of Court honor and made the trial team every semester of eligibility. He earned his Bachelor of Arts in Political Science, with a minor in Public Relations, from the University of Wisconsin-Whitewater, where he was a Dean’s List student and recipient of the UW-W Student Involvement Award.

In his spare time, Sean can be found spending time with his wife and two children, and is an avid cinephile, music lover, sports obsessive, and barbecue enthusiast.