With over two decades of experience as a litigator, Stuart concentrates his practice in the area of commercial general liability. He routinely handles high exposure matters in the fields of product liability, premises liability, auto liability, construction litigation, marine liability, dram shop and commercial litigation. This includes cases involving personal injuries and property damage claims.
As the Managing Attorney of the firm's third-largest office, Stuart oversees the daily operations, including the supervision of 75 employees. In addition to his managerial duties, Stuart serves as the Casualty Supervisor, where he ensures that all client matters are handled promptly, professionally, and effectively by the team of attorneys.
In his career, Stuart has represented manufacturers, suppliers and retailers in product liability matters, including electronics, medical equipment, food products, appliances, farm equipment, plumbing equipment, power tools, toys and sports and recreational equipment. He frequently represents property owners, retailers, pharmacies, general contractors, subcontractors and utilities in premises liability litigation. He has tried numerous cases to verdict in counties throughout Western Pennsylvania.
A significant portion of Stuart’s practice has been devoted to construction litigation. These cases are highly complex and require deep industry knowledge and experience. Stuart has handled a wide range of construction injury and defect cases, representing contractors, subcontractors, material suppliers, engineers, architects, and other construction professionals throughout Pennsylvania. His experience includes defending against claims involving construction defects such as water intrusion from faulty roofing or window and door seals, cracked foundations or improper waterproofing, structural and design issues, mold intrusion, drywall defects, and soil subsidence, heaving, or movement.
Stuart attended the University of Pittsburgh graduating with a B.A. in Political Science. He then attended the University of Pittsburgh School of Law where he participated in the Appellate Moot Court Program, Student Bar Association and the Health Law Certificate Program. He obtained his juris doctor from the University of Pittsburgh School of Law.
Stuart currently serves on the Marshall Dennehey Diversity, Equity and Inclusion Committee working to improve the recruitment, retention and advancement of diverse attorneys and professionals. He is the former President of the Pennsylvania Defense Institute, an organization of civil defense attorneys, executives of insurance companies and self-insured corporations. Stuart is also a member of the Allegheny County Bar Association and the Academy of Trial Lawyers of Allegheny County. Among his many honors, he is Rated AV Preeminent by LexisNexis Martindale-Hubbell and is recognized among the Best Lawyers in America for his work in product liability litigation. Stuart is additionally recognized as Pennsylvania Super Lawyer.
Honors & Awards
•AV Preeminent by Martindale-Hubbell
•The Best Lawyers in America, 'Lawyer of the Year,' Pittsburgh, Product Liability Litigation - Defendants (2026)
•The Best Lawyers in America, Product Liability Litigation - Defendants (2022-2026)
•Pennsylvania Super Lawyers (2018-2022; 2025-2026)
Classes/Seminars Taught
•AI in the Legal Profession, Marshall Dennehey Client Presentation, September 2024
•Civil Litigation State of Affairs - The Impact of COVID-19 in Pennsylvania and New Jersey & What’s Next, Marshall Dennehey Client Webinar, May, 2021
•An Overview of Construction Defect Litigation in Pennsylvania, Nationwide Insurance Company, December 16, 2014
•Commercial Defense Practice in New York, New Jersey & Pennsylvania, Nationwide Insurance Company, December 5, 2014
•Brief Overview of Pennsylvania Contractual Indemnity and Additional Insured Issues, Nationwide Insurance Company, April 2012
•Discoverability and Proper Use of Claim Notes, Berkley Mid-Atlantic, October 2011
Published Works
•“Yes! Waivers of Liability for Recreational Activities Are Still Effective in Pennsylvania,” Defense Digest, Vol. 23, No. 1, March 2017
•'Timing Is Everything, Even for Bad Faith Claims,' Defense Digest, Vol. 6, No. 1, February 2000
Media Commentary
•'How I Made Office Managing Partner: 'Stay True to Yourself, and Things Will Work Out to Your Benefit,' Says Stuart Sostmann of Marshall Dennehey,' Law.com, January 3, 2025
Results
Defense Verdict Following Jury Trial in Slip and Fall Case in the Court of Common Pleas of Allegheny County.
The plaintiff slipped in the lobby of a commercial building and claimed a serious and ongoing injury to her right shoulder. She alleged she fell due to a wet floor caused by the facilities management’s cleaning process and the lack of sufficient visible wet floor caution signs. The plaintiff underwent two surgeries, claimed ongoing pain and suffering, and sought $500,000 prior to trial. We represented the building ownership and the facilities management company. Problematic for the defense was the lack of a surveillance video of the incident, photographs of the lobby contemporaneous to the incident, or an incident report. Despite this, we persuaded the jury to find for the defense by establishing a consistent and credible history of habitual practice in the placement of wet floor signs in highly visible areas across the lobby. We also won the credibility battle through our well-prepared witnesses. Although faced with a sympathetic plaintiff with a substantiated history of medical treatment, our attorneys succeeded by presenting the case using “old school” personal injury defense tactics that were necessary due to the lack of video, photographs, and documentation.
Defense Verdict Secured in Slip-and-Fall Jury Trial
We obtained a defense verdict following a three-day jury trial in a slip-and-fall injury case in the Court of Common Pleas of Allegheny County. The plaintiff slipped in the allegedly wet lobby of a commercial building and claimed a serious and ongoing injury to her right shoulder. Problematic for our case was the lack of a surveillance video of the incident, photographs of the lobby contemporaneous to the incident, or an incident report. Despite this, we persuaded the jury to find for the defense by establishing a consistent and credible history of habitual practice in the placement of wet floor signs across the lobby in highly visible areas.
Thought Leadership
How I Made Office Managing Attorney: 'Stay True to Yourself, and Things Will Work Out to Your Benefit,' Says Stuart Sostmann of Marshall Dennehey
January 3, 2025
'When I was a younger attorney, I displayed arrogance at times to cover up various insecurities. My advice would be to stay true to yourself, and things will work out to your benefit.'
Defense Digest
On the Pulse...Construction Injury Litigation Practice Group
December 1, 2023
Recent data released from the United States Bureau of Labor Statistics reveals that construction laborers accounted for 11.9% of all reported fatal falls, slips, or trips in 2020 across all occupations. Sixty percent of all construction laborers perform their work near or around moving mechanical parts or in close proximity to large moving objects. Fifty percent of these workers reportedly make use of PPE. Construction sites are among the most dangerous places to work in the United States. Indeed, in 2020 alone, construction laborers accounted for 8.9% of all workplace deaths due to exposure to harmful substances or environments. With millions of accidents reported each year, injuries to construction workers are often serious or even catastrophic. This type of litigation is fraught with difficulty since it tends to involve sophisticated legal issues, multiple parties, multiple causes of action, complex relationships, and problematic factual situations. The law in this area continues to evolve as existing rules and precedent are continually challenged, overturned, replaced, or modified. Marshall Dennehey’s Construction Injury Litigation Practice Group understands these complex relationships and issues. Our firm has a significant presence in the construction industry in the representation of construction companies/prime contractors, commercial property owners/ managers, developers, design professionals, and demolition, electrical, roofing, and various other trade subcontractors in a wide array of serious loss cases where there is often catastrophic injury or death. With decades of experience, our diverse team of attorneys regularly defends our clients in a multitude of personal injury matters arising out of the construction process. We handle everything from catastrophic injury or death due to contact with objects or equipment, fatal or catastrophic transportation incidents, roofing incidents, and scaffolding/ladder incidents, to the more routine worksite slip and fall incidents. Our defense approach is aimed at the early identification of key issues and is predicated on developing the earliest possible defense strategies tailored to the individual case and client. Our involvement often begins with pre-litigation accident investigation, claims analysis, best practices related to client document and evidence retention, and early assessment of risk/liability transfer opportunities to shift liability and exposure under the terms of a construction contract, including indemnification and additional insured coverage issues. Our diverse team of trial attorneys have significant experience in handling some of the most high-profile and complex construction litigation matters taking place across the United States, and we have proven time and again, that we are ready and able to try even the most challenging construction injury matters to verdict with the skills needed to prevail. The depth of our experience is the key to our legal defense in construction injury matters. Our professionals have considerable breadth of experience in this domain. They understand the evolving and complex laws surrounding this volatile area of practice, including issues relating to insurance coverage and claims disputes, additional insured coverage, product liability, workers’ compensation, the statutory employer doctrine, contractor licensing issues, Occupational Safety and Health Act (OSHA) compliance and workplace safety issues, and the peculiar risk doctrine. Through the use of cutting-edge technology and aggressive claim investigation, we are able to assess liability exposure and potential damages issues early on in a case so, together with the client and insurer, we can effectively resolve the case. Our unique strategy and team approach consists of experienced partners, associates, and paralegals capable of handling the basic, as well as the highly-sophisticated and complex, construction injury litigation matters throughout Pennsylvania, New Jersey, Delaware, Ohio, Florida, New York, and Connecticut. We look forward to your inquiries and remain at your disposal for presentations or seminars your company may desire. Defense Digest, Vol. 29, No. 4, December 2023, is prepared by Marshall Dennehey to provide information on recent legal developments of interest to our readers. This publication is not intended to provide legal advice for a specific situation or to create an attorney-client relationship. ATTORNEY ADVERTISING pursuant to New York RPC 7.1. 2023 Marshall Dennehey. All Rights Reserved. This article may not be reprinted without the express written permission of our firm. For reprints, contact [email protected].
News
Marshall Dennehey Announces 2026 Pennsylvania Super Lawyers and Rising Stars Honorees
May 22, 2026
98 Marshall Dennehey Attorneys Recognized in the 2026 Editions of The Best Lawyers in America and the Best Lawyers: Ones to Watch in America
August 20, 2025
