Bill is a trial attorney who has litigated and tried numerous high-exposure cases in the fields of medical malpractice and general liability. He draws from his more than 20 years of experience in the area of medical malpractice defense to assist clients in achieving optimal outcomes.
As Managing Attorney and Casualty Supervisor, Bill oversees the daily operations of the office, including the supervision, mentorship, and performance management of legal and support staff. In addition to his managerial responsibilities, he ensures that all casualty matters are handled promptly, professionally, and effectively by the team of attorneys.
Bill has successfully defended a broad range of cases, including obstetrical, gynecological, surgical, oncological, pediatric, orthopedic, urologic, neurologic, gastrointestinal, psychiatric, ophthalmologic, emergency medicine, dental, podiatric and nursing. He has also represented health care providers in disciplinary hearings. Bill effectively defends clients from the inception of the case, laying the groundwork for success through motion practice, settlement and trial.
Prior to focusing his practice on medical malpractice defense, Bill worked as an Assistant District Attorney in Queens County in various bureaus, including Homicide/Investigations, Organized Crime, Appeals, Supreme Court Trial, and also as Chief of the Airport Investigations Unit. As an Assistant District Attorney, Bill tried numerous cases, argued appeals before the Appellate Division, and oversaw complex criminal investigations involving airport cargo theft and organized crime. He regularly lectured at training and education programs at the National Cargo Security Council, the Global Maritime Transportation School and the United States Merchant Marine Academy. He has also lectured before hospital staff regarding the defense of medical malpractice actions.
In addition to his firm responsibilities, Bill also serves as an Administrative Law Judge in Westchester County.
Honors & awards
New York Metro Super Lawyer
2013-2014; 2017; 2021
Year joined
2021
Thought Leadership
Marshall Dennehey’s Bill Gianaris Named Managing Attorney of the Firm’s Westchester County, NY Office
Health Care Liability
General Liability
April 23, 2025
Marshall Dennehey shareholder Bill Gianaris has been named Managing Attorney of the firm’s Westchester County, NY office.
Eight Marshall Dennehey Attorneys Selected to 2021 New York Metro Super Lawyers and Rising Stars
October 4, 2021
Eight attorneys from Marshall Dennehey’s New York City and Westchester, New York offices, and one from the firm's Mount Laurel, New Jersey office, have been selected to the 2021 edition of New York Metro Super Lawyers magazine.
AV Preeminent®: The highest peer rating standard. This rating signifies a large number of the lawyer’s peers rank him
or her at the highest level of professional excellence for their legal knowledge, communication skills and ethical standards.
Notable: This rating indicates that the lawyer has been recognized by a large number of their peers for strong ethical standards.
