Stephen O’Neil

Sheppard, Mullin, Richter & Hampton LLP

$ $$$

South Hope Street 333
Los Angeles 90071 CA US

Stephen J. O’Neil is a partner in the firm’s Los Angeles office, where he specializes in environmental law and complex environmental litigation. Mr. O’Neil has extensive experience in environmental counseling and in environmental and toxic tort litigation.

He has advised major oil companies in environmental regulatory matters, and he regularly counsels clients on the environmental implications of the purchase or sale of real property. He has tried or arbitrated numerous environmental cases, and he has extensive experience in managing large, complex environmental cases and conducting depositions and discovery.

He has conducted settlements with the United States Environmental Protection Agency, and has been engaged in complex Superfund litigation and private cost recovery actions under the Comprehensive Environmental Response, Compensation and Liability Act (“CERCLA”), the Resource Conservation and Recovery Act (“RCRA”) and various state and environmental laws. He has also appeared before numerous state and local environmental agencies.

Mr. O’Neil was co-lead trial counsel in an administrative trial relating to airborne emissions and alleged leakage from stormwater sewers at the Exide Technologies lead battery recycling facility in Vernon, California. Mr. O’Neil obtained a temporary restraining order and a preliminary injunction against the California Department of Toxic Substances Control, which reversed an order that the DTSC had issued that shut down the lead battery recycling facility with no notice.


  • J.D., University of California, Los Angeles, 1986
  • B.A., University of Notre Dame, 1983, magna cum laude


  • California
  • Federal District Courts for the Central and Eastern Districts of California
  • Federal District Court for the Northern District of Illinois
  • U.S. Court of Appeal for the Ninth Circuit


  • Member, American Bar Association
  • Member, State Bar of California (Litigation and Environmental Law Sections)
  • Member, Los Angeles County Bar Association (Litigation and Antitrust Sections)
  • Member, California Association of Business Trial Lawyers


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South Hope Street 333
Los Angeles 90071 CA US
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New York 10006 NY US