Marshall Dennehey | 14,265 followers on LinkedIn. Welcome to our company page! Founded in 1962 and headquartered in Philadelphia, PA, Marshall Dennehey, P.C. is a leading civil defense litigation law firm that represents and advises insurers, self-insured businesses, and professionals in a wide range of professional liability, casualty, health care, employment, and workers'​ compensation matters. With 500 attorneys in 19 offices throughout PA, NJ, DE, CT, OH, NY & FL Marshall Dennehey is uniquely positioned to assist clients in both avoiding litigation, as well as providing them with a vigorous defense in the event of claims and suits made against them.