Aaron R. Feigelson

Aaron R. Feigelson is a seasoned patent litigation attorney with a diverse practice, currently serving as a Shareholder at Leydig, Voit & Mayer, Ltd. in Chicago, Illinois. He joined Leydig in 2003, following his tenure as an associate at Testa, Hurwitz & Thibeault. While one tracked case shows an appearance with Fish & Richardson, current professional profiles consistently list him with Leydig.

Dr. Feigelson's practice areas primarily encompass patent, trade secret, and copyright litigation, with a particular focus on computer software and systems. His technical background, including a Ph.D. in Computer Science, underpins his ability to handle complex technology disputes. Additionally, his experience extends to chemical and process engineering, as demonstrated by his role as lead counsel for Topsoe, Inc. in an inter partes review (IPR) concerning a "Process and Plant for Preparation of Hydrogen and Separation of Carbon Dioxide" (IPR2025-01174).

He is experienced representing clients on both the plaintiff and defendant sides. While he acted as lead counsel for the petitioner (plaintiff-side) in the Topsoe IPR, he also recently secured a favorable Final Written Decision in a Post-Grant Review (PGR) for 3D Diagnostix, successfully challenging the validity of patent claims for an accused infringer. This outcome underscores his ability to represent clients facing infringement allegations. Dr. Feigelson possesses significant PTAB/IPR experience, including first-chair appearances before the Patent Trial and Appeal Board, and has argued at the Court of Appeals for the Federal Circuit. He has also been a commentator on PTAB precedential decisions, indicating his deep engagement with post-grant proceedings.

Admitted to practice in Massachusetts (2002) and Illinois (2003), Dr. Feigelson is also registered before the U.S. Patent and Trademark Office. He holds a J.D. from the University of Chicago (2002), a Ph.D. (1998) and M.S. (1995) in Computer Science from Northwestern University, and a B.A. in Mathematics from the University of Michigan (1991).