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Stuart H. Sostmann

Portrait of Stuart H. Sostmann

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.

    • University of Pittsburgh School of Law (J.D., 1999)
    • University of Pittsburgh (B.A., cum laude, 1996)
    • Pennsylvania, 1999
    • Supreme Court of the United States, 2023
    • 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 (2022-2027)
    • Pennsylvania Super Lawyers (2018-2022; 2025-2026)
    • Allegheny County Bar Association
    • American Bar Association
    • Pennsylvania Defense Institute, President 2022-2023; Executive VP of Operations 2021-2022; Executive VP of Programming 2020-2021
    • 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
    • “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 
    • Obtained a defense verdict following a three-day jury trial in a slip and fall injury case. The plaintiff slipped in the lobby of a commercial building and claimed a serious and ongoing injury to her right shoulder.  Plaintiff 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. 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 across the lobby in highly visible areas. We also won the credibility battle through our well-prepared witnesses.  Although faced with a sympathetic plaintiff with a substantiated history of medical treatment, we succeeded by presenting the case using “old school” personal injury defense tactics that were necessary due to the lack of video, photographs, and documentation.    
    • Successfully argued a precedent-setting case in the Pennsylvania Superior Court where a waiver of subrogation clause in a construction contract was applied to building damages caused by a windstorm three years after the project was completed. 
    • Successfully defended a product installer at trial in a single vehicle accident, where the placement of the product in the vehicle was claimed to be the cause of the crash at high speed.  A defense verdict was obtained after a 5 day jury trial where the demand was $800,000 prior to trial.

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 tamontemuro@mdwcg.com. 

Firm Highlights

Thought Leadership

What’s Hot in Workers’ Comp - News and Results*

RESULTS ​Perry Merlo (Harrisburg) obtained a favorable ruling involving a claimant who sustained a recognized lower back injury while employed by the defendant and continued to seek workers’ compensation benefits. Following an independent medical examination, Perry filed a termination petition alleging that the claimant had fully recovered from her work injury as of September 10, 2025. The claimant opposed the petition and presented testimony from her own medical expert. The judge granted the termination petition, finding the testimony of the defense medical expert more credible than the testimony of the claimant and her expert; and finding that the claimant had fully recovered from her work-related injury as of September 10, 2025. Kacey C. Wiedt (Harrisburg) secured a complete victory involving a alleged hand laceration resulting additional shoulder and upper extremity injuries. The defense successfully demonstrated that the claimant did not sustain the additional injuries alleged, had fully recovered from the accepted injury, and was terminated for performance-related reasons unrelated to his work injury. Relying in part on text messages and photographs that contradicted the claimant’s alleged limitations, the defense secured a decision denying the claim petition in its entirety and granting the termination petition effective June 10, 2025. The claimant recovered no additional benefits despite previously making a $230,000 settlement demand. Anthony Natale III (King of Prussia) secured a complete defense victory involving an alleged ongoing disability following a work-related cervical spine injury sustained in a truck accident. The defense successfully demonstrated that the claimant had been released to return to full-duty work, was subsequently discharged for cause after failing a mandatory drug test, and had fully recovered from his work injury. Following litigation of both the suspension and termination Petitions, the court found that the claimant was capable of returning to unrestricted employment and had fully recovered from his cervical spine injury. Anthony Natale III (King of Prussia) secured a complete defense victory involving an allegation of ongoing orthopedic and neurological injuries, including post-concussion syndrome, resulting from a motor vehicle accident while volunteering for the township. The defense successfully demonstrated that the claimant had fully recovered from her work-related injuries and was exaggerating her symptoms. Finding the defense medical expert more credible, the court granted the termination petition and concluded that the claimant had fully recovered. The court also dismissed all four of the claimant’s review petitions challenging prior utilization review determinations that found her medical treatment to be unreasonable and unnecessary. Anthony Natale III (King of Prussia) secured a complete defense victory involving a low back injury. The defense successfully demonstrated through medical evidence that the claimant had fully recovered from her work injury. Following litigation of the termination petition, the court found the defense expert credible and concluded that the claimant was fully recovered. The court granted the termination petition despite the claimant proceeding without counsel and arguing that personal circumstances prevented her from adequately defending the matter. As a result, the claimant’s entitlement to ongoing workers’ compensation benefits was terminated. . *Prior Results Do Not Guarantee a Similar Outcome NEWS Congratulations to Kacey Wiedt on being named Best Lawyers in America® 2027 "Lawyer of the Year." We are also proud to celebrate our firm’s 14 workers’ compensation attorneys who have been recognized in the 2027 editions of The Best Lawyers in America® and Best Lawyers: Ones to Watch® in America. This distinction is especially meaningful, as fewer than 6% of practicing attorneys in the United States earn recognition from their peers through the Best Lawyers selection process. The Best Lawyers in America® Heather Byrer Carbone Daniel W. Deitrick Benjamin K. Durstein Linda Wagner Farrell Keri L. Morris-Johnston Anthony Natale III Michele R. Punturi Andrea C. Rock Robin M. Romano Robert P. Schenk Michael A. Sebastian Francis X. Wickersham A. Judd Woytek Best Lawyers: Ones to Watch® in America Alana Staniszewski Angela DeMary (Mount Laurel) is presenting at the National African American Insurance Association (NAAIA) Annual Conference on September 24. In a panel workshop session, "Old Instincts, New Tools: How AI is Actually Transforming Claims Handling," Angela will discuss existing and emerging AI techniques relevant to claims and legal defense, and explore how AI works alongside traditional methods to improve efficiency and outcomes. For more information, click here. Judd Woytek (King of Prussia) is speaking at the National Comp conference in Las Vegas in September. He joins a group of panelists to present “Older, Wiser, But Costlier to Heal: What an Aging Workforce Means for Employers and for the Industry,” a discussion focused on the challenges employers face in balancing safety, compliance, and productivity as the workforce continues to age. Judd and his co-presenters will address proactive strategies to reduce workplace risk, support older employees, navigate age-discrimination and workers’ compensation issues, and build a safer, more resilient workforce. For more information, visit National Comp. Conference and Trade Show.

News

106 Marshall Dennehey Attorneys Recognized in the 2027 Editions of The Best Lawyers in America® and the Best Lawyers: Ones to Watch® in America

Marshall Dennehey is proud to highlight the firm’s 106 attorneys who have been recognized in the 2027 editions of The Best Lawyers in America® and the Best Lawyers: Ones to Watch® in America. Less than 6% of all practicing lawyers in the U.S. were selected by their peers for this recognition. Additionally, four of the firm’s attorneys received the Best Lawyers® 2027 “Lawyer of the Year” awards in their respective practice areas and demographic regions. Since it was first published in 1983, Best Lawyers® has become universally regarded as the definitive guide to legal excellence. Best Lawyers lists are compiled based on an exhaustive peer-review evaluation. For more information, please visit https://www.bestlawyers.com/. OUR 2027 LAWYERS OF THE YEAR Harrisburg, PA Christopher Reeser, Personal Injury Litigation - Defendants Kacey Wiedt, Workers Compensation Law - Employers Roseland, NJ Justin F. Johnson, Medical Malpractice Law - Defendants Leonard Leicht, Personal Injury Litigation - Defendants   OUR 2026 BEST LAWYERS IN AMERICA Philadelphia, PA Nicholas D. Bowers, Personal Injury Litigation - Defendants Josh J. T. Byrne, Professional Malpractice Law - Defendants Jefferey J. Chomko, Insurance Law James H. Cole, Insurance Law John J. Delany III, Personal Injury Litigation - Defendants Laurianne Falcone, Personal Injury Litigation - Defendants John P. Gonzales, Employment Law - Management John Hare, Appellate Practice Daniel D. Krebbs, Personal Injury Litigation - Defendants Michele Punturi, Workers' Compensation Law - Employers Bradley D. Remick, Product Liability Litigation - Defendants Andrea Cicero Rock, Workers' Compensation Law - Employers Robin M. Romano, Workers' Compensation Law - Employers Daniel J. Ryan, Jr., Personal Injury Litigation - Defendants Gary M. Samms, Professional Malpractice Law - Defendants Christopher N. Santoro, Personal Injury Litigation – Defendants; Product Liability Litigation -Defendants Josh D. Scheets, Personal Injury Litigation - Defendants Robert P. Schenk, Workers' Compensation Law - Employers Robert E. Smith, Insurance Law Robin Snyder, Litigation - Health Care Michael L. Turner, Commercial Litigation; Criminal Defense: White-Collar; Mass Tort Litigation / Class Actions - Defendants Claire Breaux Ventola, Product Liability Litigation - Defendants Pittsburgh, PA Melissa Devich Cochran, Commercial Litigation; Mass Tort Litigation / Class Actions – Defendants; Product Liability Litigation - Defendants  John F. Deasy, Personal Injury Litigation – Defendants; Product Liability Litigation - Defendants Daniel W. Deitrick, Workers' Compensation Law - Employers Douglas C. LaSota, Litigation - Construction; Mass Tort Litigation / Class Actions - Defendants Joseph V. Lesinski, Product Liability Litigation – Defendants   Christian D. Marquis, Personal Injury Litigation - Defendants Patricia A. Monahan, Insurance Law; Litigation - Insurance Patrick T. Reilly, Commercial Litigation; Mass Tort Litigation / Class Actions – Defendants; Product Liability Litigation - Defendants Brett C. Shear, Medical Malpractice Law - Defendants Teresa O. Sirianni, Education Law; Employment Law – Management; Litigation - Labor and Employment Stuart Sostmann, Product Liability Litigation – Defendants Danielle M. Vugrinovich, Mass Tort Litigation / Class Actions - Defendants Scranton, PA Sarah E. Argo, Litigation - Insurance Michael J. Connolly, Personal Injury Litigation – Defendants; Professional Malpractice Law - Defendants Matthew Keris, Litigation - Health Care; Medical Malpractice Law - Defendants John T. McGrath, Jr., Insurance Law; Medical Malpractice Law – Defendants; Product Liability Litigation - Defendants William J. McPartland, Insurance Law John R. Nealon, Product Liability Litigation - Defendants Victoria Scanlon, Health Care Law; Litigation - Health Care; Medical Malpractice Law - Defendants Michael A. Sebastian, Workers' Compensation Law - Employers Thomas A. Specht, Insurance Law; Litigation - Insurance Suzanne Tighe, Litigation Insurance Harrisburg , PA Casey Alan Coyle, Administrative/Regulatory Law; Appellate Practice; Commercial Litigation Brittany E. Bakshi, Personal Injury Litigation - Defendants Shannon P. Fellin, Workers' Compensation Law - Employers Allison Krupp, Insurance Law John R. Ninosky, Litigation – Insurance; Personal Injury Litigation - Defendants Christopher Reeser, Personal Injury Litigation - Defendants Kacey Wiedt, Workers' Compensation Law – Employers King of Prussia, PA  Michael L. Detweiler, Construction Law Joseph L. Hoynoski III, Medical Malpractice Law - Defendants Gregory J. Kelley, Construction Law, Litigation - Construction Anthony Natale III, Workers' Compensation Law - Employers Francis X. Wickersham, Workers' Compensation Law - Employers A. Judd Woytek, Workers' Compensation Law – Employers Erie, PA Patrick M. Carey, Personal Injury Litigation - Defendants Joel M. Snavely, Health Care Law; Insurance Law New Haven, CT Michael Wrona, Commercial Litigation, Litigation - Bankruptcy  Mount Laurel, NJ David D. Blake, Litigation - Insurance Barbara Davis, Personal Injury Litigation - Defendants Lynne Nahmani, Litigation - Health Care John H. Osorio, Personal Injury Litigation - Defendants John L. Slimm, Legal Malpractice Law – Defendants; Professional Malpractice Law – Defendants Roseland, NJ Robert T. Evers, Medical Malpractice Law - Defendants Justin F. Johnson, Medical Malpractice Law - Defendants Julia Klubenspies, Medical Malpractice Law - Defendants Leonard C. Leicht, Personal Injury Litigation - Defendants Patricia M. McDonagh, Appellate Practice Sunny Sparano, Litigation - Construction Randall S. Watts, Health Care Law New York, NY Tonya M. Lindsey, Medical Malpractice Law - Defendants Tampa, FL Michael Archibald, Personal Injury Litigation - Defendants Lindsay G. McCormick, Litigation – Construction Orlando, FL Thomas F. Brown, Personal Injury Litigation - Defendants Dante C. Rohr, Commercial Litigation Fort Lauderdale, FL Kimberly Kanoff Berman, Appellate Practice Patrick M. Delong, Personal Injury Litigation – Defendants Jacksonville, FL  Heather Byrer Carbone, Workers' Compensation Law - Employers Linda Wagner Farrell, Workers' Compensation Law - Employers Elizabeth B. Ferguson, Litigation - Construction James P. Hanratty, Personal Injury Litigation – Defendants Wilmington, DE Sarah B. Cole, Litigation - Insurance Benjamin K. Durstein, Workers' Compensation Law - Employers Maria R. Granaudo, Medical Malpractice Law - Defendants  Keri L. Morris-Johnston, Workers' Compensation Law - Employers Cincinnati, OH Timothy B. Schenkel, Personal Injury Litigation - Defendants David E. Williamson, Personal Injury Litigation - Defendants Cleveland, OH Vincent E. Cononico, Litigation – Insurance, Personal Injury Litigation - Defendants Jillian L. Dinehart, Personal Injury Litigation - Defendants David J. Fagnilli, Insurance Law Jason P. Ferrante, Health Care Law, Litigation - Health Care Andrew H. Isakoff, Transportation Law Leslie M. Jenny, Litigation - Health Care; Medical Malpractice Law – Defendant OUR 2026 BEST LAWYERS: ONES TO WATCH Jacksonville, FL Sean J. Reeves, Personal Injury Litigation – Defendants; Product Liability Litigation - Defendants Orlando, FL Carolin A. Pacheco, Insurance Law Mount Laurel Stacey Gorin, Insurance Law Melville, NY Kimberly Gitlin, Personal Injury Litigation – Defendants Matthew A. Gray, Insurance Law; Personal Injury Litigation - Defendants Philadelphia, PA Holli K. Archer, Health Care Law; Medical Malpractice Law – Defendants; Professional Malpractice Law Emily Pritchyk, Commercial Litigation; Product Liability Litigation – Defendants Pittsburgh, PA Taylor E. Kosko, Mass Tort Litigation / Class Actions – Defendants; Personal Injury Litigation - Defendants Alana Staniszewski, Workers' Compensation Law - Employers Michael D. Winsko, Product Liability Litigation – Defendants; Transportation Law King of Prussia, PA Richard Lechette, Commercial Litigation; Insurance Law, Personal Injury Litigation – Defendants