Biography

Daniel R. Sonneborn is a Director in the firm's Litigation Practice Group, working primarily from the firm’s Boston office. A negotiator and litigator, his clients include those in professional services and regulated industries like transportation, insurance, health care, financial services, and construction. Dan’s counsel ranges in focus from professional liability and risk mitigation to multi-jurisdictional class actions. He has developed a particular interest in transportation law, and represents motor carriers, brokers, freight forwarders, and insurance companies in transportation-related matters and litigation, including cargo loss and damage, warehousing, contractual issues, and employment matters.

Despite his upbringing in a family of medical providers, Dan found his professional path in law school, where he was able to combine his generational connection to medicine with his passion for problem-solving. He served as Managing Editor of Suffolk Law’s Journal of Health and Biomedical Law, and continues to advise healthcare professionals to this day. His deep New England roots are reflected in his experience appearing in state and federal courts in Massachusetts, Maine, and New Hampshire.  

Dan lives in Medford, Massachusetts, with his wife and two children.

Professional Activities

  • Massachusetts Defense Lawyers Association
  • Transportation Lawyers Association
  • Conference of Freight Counsel

Honors & Recognition

  • Massachusetts Super Lawyers Rising Star, Transportation/Maritime – 2016 - 2021

Civic and Charitable Activities

  • Coach, Medford Youth Hockey and Baseball

Publications

  • Co-author, Introduction, A Practical Guide to Understanding RSA 358-A in New Hampshire (MCLE New England, 1st Edition, 2014).

Firm Highlights

Publication

Maine DEP Issues PFAS in Products Concept Draft Rule

The Maine DEP’s PFAS in Products Program has released its long-awaited Chapter 90 concept draft language (the “PFAS in Products Rule”) for implementation of Maine’s recently-amended “PFAS in Products Law.” The concept draft provides...

Publication

Copyright Litigation: Substantial Similarity

In copyright litigation, courts assess substantial similarity to determine if alleged copying constitutes infringement. This evaluation involves comparing works across different categories using objective measures and subjective impressions to weigh similarities and dissimilarities. Even when...

Event

2024 Maine Employment Law Summit

Join us for Preti Flaherty's 2024 Maine Employment Law Summit! For almost three decades, Preti Flaherty's Employment Law team has delivered practical insights and best practices to Maine employers at our annual fall Employment...

Press Coverage

Looking to 'new generation,' Preti Flaherty promotes 42-year-old litigator to managing partner

Effective July 15, Michael S. Smith has been named managing partner of the law firm Preti Flaherty. Michael succeeds David Van Slyke, who will resume his role as chair of the firm’s environmental practice...

Press Coverage

Portland law firm Preti Flaherty unveils renovated HQ space

Preti Flaherty has remodeled its Portland headquarters, spanning three floors and 41,000 square feet at One City Center. The update features hybrid workstations, collaborative areas, and an internal staircase that integrates flexible conference and...

Publication

Recent Massachusetts Appeals Court Decision Holds that Construction Defects Are Not Covered by CGL Policy

The recent Massachusetts Appeals Court decision in Lessard v. R.C. Havens & Sons, Inc. (August 2024) offers important clarification for contractors, subcontractors, and insurers regarding the coverage of construction defects under commercial general liability...

News

Preti Flaherty Names Michael S. Smith as Managing Partner

Preti Flaherty announced this week the election of Michael S. Smith as the firm’s new Managing Partner, effective July 15, 2024. He succeeds David Van Slyke, who is resuming his role as chair of...

News

36 Preti Flaherty Attorneys, including 4 “Ones to Watch” Recognized by National Directory

Thirty-six Preti Flaherty attorneys, including four “Ones to Watch,” have been named to Best Lawyers in America 2025, a highly regarded directory of attorneys and law firms in the United States. The individual attorneys...

News

Matthew C. Worthen Joins Preti Flaherty’s Real Estate and Finance Practice Group

Preti Flaherty is pleased to welcome Matthew C. Worthen as a Director in the firm’s Real Estate and Finance Group. Worthen previously served as a Shareholder and Chair of the Real Estate Group at...

Publication

Supreme Court Clarifies Constitutionality of Outdoor Camping Bans

Earlier today the United States Supreme Court issued its decision in the  City of Grants Pass, Oregon v. Johnson et al. , overturning a 2019 decision from the 9 th  Circuit Court, which held...