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O'Connor & Semmerling Law Group, LLC
711 West Grand Avenue
Suite 303
Chicago, IL 60654

Attorney Profile

Tim Jon Semmerling


Tim Jon Semmerling firmly believes that humanizing his clients to juries and the courts is an essential aspect of winning in every trial. He views each case as two significant phases: (1) fighting to protect the client’s innocence, and (2) preparing a safety net for the client to drive down sentencing in the event of a guilty verdict. As a mitigation expert, Mr. Semmerling has been appointed in some of the largest criminal cases involving the death penalty in the U.S. military. He has also worked extensively with the Cook County Public Defender’s Office to reduce potential sentences.

Through the Center for Justice in Capital Cases at DePaul University, Mr. Semmerling has contributed research to the Capital Jury Project, an academic study of jury decision-making and behavior in death-penalty cases. He has trained at the Clarence Darrow Death Penalty Defense College’s Mitigation Program (Chicago, Illinois) and the Trial Lawyers College’s Death Penalty Seminar (Dubois, Wyoming). Mr. Semmerling has also worked for the Council of American Islamic Relations as a Civil Rights Legal Research Fellow. Because of his unique knowledge and experience in such issues as Middle East culture, the War on Terror, and criminal sentencing, he is regularly requested to present at training seminars for lawyers and at academic conferences.  

Mr. Semmerling is a founding partner in The Mercury Endeavor, LLC, a mitigation and sentencing advocacy firm.  He has previously clerked for the County Public Defender Office’s Felony Trial Division and Homicide Task Force.

Contact Information
Phone: 312.981.9084
Fax: 312.929.3136


DePaul University College of Law, Chicago, Illinois (J.D., 2009) Certificate in Criminal Law

Indiana University, Bloomington, Indiana (Ph.D., Near East Languages & Cultures, conferred with distinction, 2000)

University of Texas at Austin, Austin, Texas (M.A., Middle East Studies, 1994)

Northeastern University, Boston, Massachusetts (B.S., Finance & Marketing, conferred with high honors, 1984)

Bar Admissions

Professional Memberships
American Bar Association
Chicago Bar Association
Illinois Association of
Criminal Defense Lawyers
Illinois State Bar Association
National Association of Criminal Defense Lawyers