Colleen O’Brien


Contact information

Phone: (213) 239-5622
Fax: (213) 239-5623

Trial attorney and litigator Colleen O’Brien tries and resolves lawsuits and challenges related to toxic torts, catastrophic injury and complex employment matters. Her experience includes leading a range of civil litigation, from consumer fraud to defamation to chemical exposure and personal injury claims. Colleen defends companies against plaintiffs’ sophisticated claims involving long-term occupational injury, infectious disease, property damage and groundwater contamination. A former military prosecutor, Colleen guides business clients as first chair, lead counsel in bench and jury trials in state and federal courts throughout the United States.

Trial-strength litigation counsel

Colleen has successfully tried more than 30 matters to verdict for her clients, both as a government attorney in criminal contexts and in private practice. She is known for her skillful preparation and examination of medical and technical experts at deposition and trial. Her keen attention to details and commitment to cases have helped clients settle their disputes efficiently and quickly – and avoid lengthy and costly trials.

A former military prosecutor, Colleen guides business clients as first chair, lead counsel in more than 30 bench and jury trials in state and federal courts throughout the United States.

Her current emphasis on defending product liability litigation focuses on claims by former workers of injuries caused by occupational exposures to hydrocarbon solvents and other workplace chemicals. In addition, on the employment law front, Colleen has defended numerous allegations of wrongful termination and discrimination for corporate clients.

Professional leadership

Earlier in her career, Colleen served with the U.S. Coast Guard at Alameda, California, where she gained valuable experience as a procurement attorney-advisor, environmental attorney, claims & litigation attorney, and prosecutor. In these roles, Colleen evaluated millions of dollars of affirmative and defensive claims for liability, litigation risk, valuation and referral to the U.S. Department of Justice.

Colleen is a magna cum laude graduate of the University of Pittsburgh and later graduated from its school of law. She served as an enlisted Army reserve radio operator and then went on to become a Coast Guard JAG officer and boarding team member.

In her pro bono practice, Colleen has worked on numerous immigration cases, including successful applications for asylum and visas for LGBTQ individuals and international victims of trafficking, gang violence and domestic abuse. Colleen also serves as a volunteer in the Los Angeles Public Library’s Adult Literacy Program.

Representative achievements

  • Obtained pleadings-stage dismissal of fraudulent concealment and negligence claims, on behalf of a refinery client, based on workers’ compensation exclusivity.
  • Obtained summary adjudication of negligence and products liability claims involving a former gasoline tanker truck driver based on a statute of limitations defense.
  • Achieved a dismissal at the pleadings stage of a 16-plaintiff, fear-of-cancer case involving alleged exposures to hexavalent chromium.
  • Prevailed for plaintiffs, obtaining a verdict in a two-week jury trial involving libel and infliction of emotional distress.
  • Won the appeal of an anti-SLAPP motion in a case involving limited public figures.
  • Secured an appellate victory in a breach of contract/fraud case involving real estate developer misrepresentations.
  • Served on the trial team related to the criminal investigation and prosecution of a major San Francisco Bay oil spill case, resulting in federal, corporate and individual convictions and a $9.4 million settlement. Received Certificate of Commendation from the U.S. Department of Justice.


  • J.D., University of Pittsburgh, School of Law
    • Order of the Barristers; Appellate Moot Court Board; National Moot Court Team; Appellate Competition Award
  • B.A., University of Pittsburgh, magna cum laude
Bar and court admissions
  • State Bar of California
  • United States District Court, Central District of California
  • United States District Court, Eastern District of California
  • United States District Court, Northern District of California
  • United States Court of Appeals, Ninth Circuit

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