Karl advocates on behalf of wrongfully convicted clients attempting to secure post-conviction relief in in state and federal courts. This involves extensive written, courtroom, and appellate litigation, interviewing witnesses and investigating cases, and fact and expert discovery. As a Lecturer in the Exoneration Project's clinic at the University of Chicago Law School, Karl supervises law students in the representation of innocent, wrongfully-convicted clients and teaches a clinical seminar on post-conviction advocacy.

Karl was a litigation associate in Winston & Strawn's Chicago office. He concentrated his practice on intellectual property matters, commercial disputes, and appellate litigation.Karl’s pro bono activities included the representation of wrongfully-convicted individuals seeking post-conviction relief. He helped secure the release of a client wrongfully imprisoned for 24 years; the release of another client wrongfully imprisoned for 21 years; and helped clients secure Certificates of Innocence clearing their names. Karl also defended clients in federal criminal matters.