Lyle is Co-Head of US Securities & Shareholder Litigation. He represents companies, officers, and directors in securities cases and Securities and Exchange Commission (SEC) enforcement matters throughout the United States. He also conducts corporate internal investigations and counsels clients with respect to securities regulatory issues.

Lyle represented Mark Cuban in obtaining a complete victory against the SEC in Cuban’s closely watched insider trading case. He also represents, or has represented, a number of prominent companies in the defense of securities class actions, including Paramount Global, PayPal, Opendoor, Lumen Technologies/CenturyLink, Northrop Grumman, Fidelity National Financial, and Lumber Liquidators.

Lyle is the author of the well-known blog, The 10b-5 Daily, which tracks key developments in securities litigation, and is the co-chairman of the annual Practicing Law Institute securities litigation program. He also co-edits “Securities Litigation: A Practitioner’s Guide,” the leading treatise in this area of the law.

Finally, Lyle frequently submits amicus briefs in prominent securities litigation cases on behalf of the Washington Legal Foundation (WLF) and other well-known organizations, including recent briefs in the U.S. Supreme Court in the Macquarie Infrastructure, Goldman Sachs, Emulex, Halliburton, and ANZ Securities cases. His brief on behalf of WLF in the ANZ Securities case was cited in the Court’s opinion.


Representative matters

Opendoor in a securities class action based on alleged pricing system failures. Obtained dismissal.

Paramount Global in a securities class action in connection with the collapse of Archegos Capital Management. Obtained dismissal.

ChannelAdvisor in a securities class action based on missed financial guidance. Obtained dismissal and affirmed on appeal.

Alcobra in a securities class action against a life sciences company based on alleged misstatements related to a drug trial. Obtained dismissal.

Published Work

  • Author, Co-Editor, Securities Litigation: A Practitioner’s Guide, PLI Press, 2023
  • Author, “Fixing the Insider Trading Prohibition Act,” The Hill, 2021
  • Author, “The Ninth Circuit’s Recent Decisions on the Pleading of Loss Causation in Securities Fraud Cases,” Securities & Commodities Regulation, Vol. 54 No. 10, 2021
  • Author, “Justices Should Clarify Securities Fraud Loss Causation,” Law360, 2021

Speaking Engagements

  • Co-chairman, Securities Litigation: From Investigation to Trial, Practising Law Institute, New York, 2009 to present
  • Speaker, Storming the Gatekeepers: When Compliance Officers and In-House Lawyers Are at Risk, Practicing Law Institute, 2021 and 2023
  • Speaker, NYC Bar, Insurers’ and Insureds’ Perspectives on Current Issues in D&O Liability and Insurance, May 2019
  • Speaker, NYCLA Securities Litigation & Regulatory Enforcement Conference: Insights for the Financial Services Attorney, April 2015

Leadership Positions And Professional Affiliations

  • Advisory Board, Securities Reform Act Litigation Reporter.
  • Adjunct professor, George Mason University School of Law (2003-2005).
Thoughtful and a great professional, he’s a pleasure to work with” and “a total pro - he knows the area.
Chambers USA


  • Ranked in Band 1 for securities litigator, Chambers USA
  • Recognized as a “Litigation Star” by Benchmark Litigation



Maryland, 1998
District of Columbia, 1999
Virginia, 2000
New York, 2017


United States Supreme Court, 2006
United States District Court for the District of Maryland, 1998
United States District Court for the Eastern District of Virginia, 2001
United States District Court for the Western District of Virginia, 2004
United States District Court for the District of Columbia, 2009
United States District Court for the Southern District of New York, 2017
United States Court of Appeals - District of Columbia Circuit, 2012
United States Court of Appeals for the Second Circuit, 2022
United States Court of Appeals for the Fourth Circuit, 2001
United States Court of Appeals for the Fifth Circuit, 2009
United States Court of Appeals for the Eighth Circuit, 2022


B.A., John Hopkins University, 1993
M.A., John Hopkins University, 1993, Paul H. Nitze School of Advanced International Studies (SAIS)
J.D., University of Chicago, 1996
A&O Shearman was formed on May 1, 2024 by the combination of Shearman & Sterling LLP and Allen & Overy LLP and their respective affiliates (the legacy firms). Any matters referred to above may include matters undertaken by one or more of the legacy firms rather than A&O Shearman.