Founding Partner of Leon Cosgrove, LLC


DEREK E. LEON is a founding partner of Leon Cosgrove, LLC and a Chamber-Ranked Commercial Litigator who has tried numerous complex cases to verdict in state and federal courts across the country.

Mr. León is praised by Chambers for his “wide range of litigation and trial skills,” including his “excellent sense of strategy” and oral advocacy skills. Chambers also underscores his expertise in complex disputes “across a wide array of sectors, including financial services, manufacturing, technology and real estate.”

In addition to his twenty (20) years of first-chair trial experience in both state and federal courts across the nation, Mr. León also has first-chair arbitration experience in national and international arbitration forums. He also has handled appeals in both state and federal courts in a number of jurisdictions.

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Founding Partner of Leon Cosgrove, LLC


LAURIE U. MATHEWS is a partner at Leon Cosgrove, LLC where she focuses her practice on complex commercial and business litigation in federal and state course nationwide.

Ms. Mathews litigates complex contractual disputes, and claims involving non-compete covenants, trade secrets and deceptive business practices, consumer product defects and franchise and distributor relationships.

Prior to joining León Cosgrove, Ms. Mathews was a partner in the Miami office of Hunton & Williams, LLP, where she represented many of that firm’s institutional clients in the consumer products and financial sectors.

Ms. Mathews also has significant experience in corporate governance, designing and implementing corporate compliance programs and conducting internal investigations on a variety of issues, including money laundering.

Ms. Mathews graduated from Harvard University, cum laude, in June, 1993; and received her Juris Doctor, magna cum laude, from University of Miami School of Law, in May, 1997


Founding Partner of Leon Cosgrove, LLC


JOHN R. BYRNE is a partner at Leon Cosgrove, LLC where he focuses his practice on commercial litigation and appellate matters.

Mr. Byrne specializes in the litigation of complex commercial transactions and consumer fraud matters on behalf of both plaintiffs and defendants.

Prior to joining León Cosgrove, he was an Assistant United States Attorney for the Southern District of Florida. During his time at the U.S. Attorney’s Office, Mr. Byrne charged over 60 cases, including numerous fraud cases. He took 16 of these cases to trial, serving as first chair ten times and second chair six times. During his time as a prosecutor, he developed an extensive knowledge of federal law, including federal statutory law, the Federal Rules of Evidence, and the Federal Rules of Criminal Procedure.

Mr. Byrne also has extensive federal appellate experience. In addition to having argued a case before the U.S. Court of Appeals for the Eleventh Circuit, he served as the law clerk to Chief Judge Jeffrey R. Howard of the U.S. Court of Appeals for the First Circuit.

Mr. Byrne graduated from the University of Florida, cum laude, in May, 2002; and received his Juris Doctor, cum laude, from Cornell Law School in May, 2007.



Marcos Daniel Jiménez is a prominent trial lawyer with a proven track record of success in complex business litigation and white-collar criminal defense matters Marcos previously served as the United States Attorney for the Southern District of Florida, leading approximately 230 prosecutors in an active and important region for federal criminal cases.

Chambers USA has described Marcos as “a great trial lawyer, fearless in the courtroom, which makes him a dangerous opponent The National Law Journal featured him in its annual “ issue for his trial victory on behalf of Verizon Wireless in a deceptive trade practices case brought by the Florida Attorney General In addition to maintaining a thriving legal practice, Marcos is an active community and bar leader He previously served on the Board of Trustees of Baptist Health Systems, Florida’s largest nonprofit healthcare organization.

Marcos graduated in the top one percent of his class at the University of Miami School of Law and is a member of Iron Arrow, the University’s highest honor.