Mr. Fitzsimmons successfully represented Pittsburgh Steeler and NFL Hall of Famer Mike Webster in his disability lawsuit against the NFL, beginning in 1997. This was the first time anyone had alleged and proved that traumatic football-related activities caused brain injury—Chronic Traumatic Encephalopathy (CTE). Along with Dr. Julian Bailes and Dr. Bennet Omalu, he Co-Founded the Brain Injury Research Institute (BIRI) in 2007, serving as Co-Director with Dr. Jenn Hammers. 

Mr. Fitzsimmons received a BS degree from Allegheny College in Meadville, Pennsylvania, and his Juris Doctorate from the University of Baltimore School of Law.