.

G. Mark Thompson

President & CEO

Chairman, Executive Committee

GMThompson@mdwcg.com

Portrait of G. Mark Thompson

As President and CEO of Marshall Dennehey, Mark is responsible for the day-to-day management and business strategy of the firm which consists of 500 attorneys operating out of 19 offices throughout Pennsylvania, New York, New Jersey, Connecticut, Delaware, Ohio and Florida. He was elected to the position in December of 2017 after serving more than three years on the Executive Committee and a decade on the Board of Directors. He succeeded Tom Brophy who served in the role for 13 years.

Mark is joined by a management team comprised of two other senior executives, a Board of Directors, managing attorneys from every office, practice group supervisors, administrative directors and over 1,000 employees who combine their talents to develop and implement the strategies and achieve the objectives of the firm and its clients.

Prior to moving to the firm's Philadelphia headquarters in 2014, Mark also served as the regional managing attorney for its four Florida offices. A Florida native, it was there he built a reputation as a "go to" attorney advising Fortune 500 clients in high profile, high exposure and often crisis  situations. During his career he has handled matters that attracted international media attention, are the subject of books, a documentary film and in one instance a hearing before the US House of Representatives in Washington DC, at which Mark represented one of the corporations testifying.

Mark has more than 30 years of experience in the legal profession, is rated AV Preeminent by Martindale Hubble, was recognized in 2006, 2007, 2013 and 2014 as a Florida Super Lawyer and in 2012 as one of Florida's Legal Elite by Florida Trend magazine. He is admitted to practice before the Florida Supreme Court, the United States Court of Appeals for the Eleventh Circuit and the United States District Court for the Middle District of Florida. He has tried cases in county, circuit, and federal courts and argued before the District Courts of Appeal. In 2012 he also became licensed to practice in Pennsylvania.

Prior to attending law school, Mark spent two years working as an insurance adjuster. The experience continues to inform his understanding of the critical needs of claims professionals.

His civic activities include serving on the Board of Directors of Christian Legal Clinics of Philadelphia, a legal aid organization assisting the disadvantaged, whose north Philadelphia clinic was started and is staffed every month by Mark and his colleagues from Marshall Dennehey. Mark also has served on the Grants Committee of the Philadelphia Bar Foundation.

    • Cumberland School of Law (J.D., 1989)
    • University of Florida (B.A., 1984)
    • Florida, 1989
    • U.S. District Court Middle District of Florida, 1990
    • U.S. Court of Appeals 11th Circuit, 1998
    • Pennsylvania, 2012
    • Supreme Court of the United States
    • AV® Preeminent™ by Martindale-Hubbell®
    • Florida Super Lawyers (2006-2007, 2013-2014)
    • Florida Trend Magazine's Florida Legal Elite, 2012
    • Pennsylvania Super Lawyers (2018-2022)
    • Claims & Litigation Management Alliance (CLM)
    • Defense Research Institute
    • International Amusement & Leisure Defense Association
    • International Association of Amusement Parks and Attractions (IAAPA)
    • Orange County Bar Association
    • The Best Offense is a Good Defense: Managing Liability Claims in Today's Litigious Environment, Business Insurance Webinar, August 12, 2015
    • The Claim Management Link: Interplay Between Risk Tolerance, Operational Structure, Litigation and Claim Outcomes, CLM Annual Conference, March 2015
    • Florida Premises Liability - Investigation and Defense
    • Florida Liquor Liability
    • Spoliation of Evidence
    • Defended a corporation and obtained summary judgments in multiple federal lawsuits alleging sponsorship, production, distribution and sale of videos depicting plaintiffs' underage participation in various spring break contests.
    • Defended a manufacturer and obtained satisfactory confidential resolution of claims brought by 51 factory employees alleging toxic exposure.
    • Defended a state agency and obtained defense verdict in wrongful death trial alleging inadequate traffic control.
    • Defended a major insurer and obtained defense verdict in trial brought by owner of an oddities museum whose collection and building was completely destroyed by fire.
    • Defended a tourist destination and obtained summary judgment in a negligence action brought by a contracted performer rendered quadriplegic as a result of an accident during a gymnastic slam dunk exhibition.
    • Defended a company and obtained defense verdict on appeal in lawsuit alleging bottle "exploded" while being handled by plaintiff.
    • Defended a tourist destination and obtained defense verdict in trial alleging inadequate slip resistance of drainage grates.
    • Defended and settled numerous lawsuits involving tractor trailer rollovers allegedly caused by improper loading of cargo.
    • For nearly 20 years, defended theme parks and tourist destinations throughout Florida in hundreds of cases involving amusement rides, wild animals, negligent security, E-coli outbreaks, slip and falls, defamation, food poisoning, false imprisonment and matters of intellectual property.
    • Anheuser-Busch, Inc. v. Lenz, 669 So.2d 271 (Fla. 5th DCA 1996)
    • Becton v. Metal Container Corp., 856 So.2d 982 (Fla. 1st DCA 2003)
    • Jordan v. Sea World of Florida, Inc., 938 So.2d 991 (Fla. 5th DCA 2006)
    • Badillo v. Anheuser-Busch, 19 Fla. L. Weekly Fed. D 641 (M.D. Fla. 2006)

Thought Leadership

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Media Commentary

G. Mark Thompson Quoted in The American Lawyer Article on Staffing in Defense Industry

August 15, 2024

Media Commentary

Marshall Dennehey President & CEO Featured on Cover of Best's Review

May 1, 2024

Marshall Dennehey President & CEO G. Mark Thompson was featured on the cover of the May 2024 issue of Best's Review and quoted in the article, "For the Defense."

News

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Firm Highlights

Result

Summary Judgment Secured, Preserving $750,000 in Coverage for Insured in Major Trucking Liability Dispute

Ray Freudiger and Michael A. Roberts (both of Cincinnati) successfully obtained summary judgment on behalf of their client in a coverage dispute arising from a May 19, 2022, motor vehicle accident. A permissive driver operated a box truck for an interstate trucking company and caused severe injuries to two tort victims. Prior to the accident, the insured had procured a commercial auto policy for the trucking company with stated limits of $1,000,000. Following the accident, the insurer initiated a declaratory judgment action asserting that only reduced bodily injury limits of $25,000/$50,000 applied and later counterclaimed, alleging it would not have insured the driver had he been properly submitted for approval under the policy. After extensive discovery, briefing, and oral argument, the court rejected the insurer’s attempt to shift responsibility for the $750,000 in coverage it was legally required to provide for permissive drivers under Ohio law, granting summary judgment in favor of the insured and preserving $750,000 in liability exposure.

Marshall Dennehey Announces 2026 Ohio Super Lawyers and Rising Stars

News

Marshall Dennehey Announces 2026 Ohio Super Lawyers and Rising Stars

Portrait of Carolyn Schweizer, with text below: Philadelphia Office Managing Attorney

News

Marshall Dennehey Names Carolyn Schweizer New Philadelphia Office Managing Attorney

Result

No-Cause Jury Verdict Secured in Wrongful Death Trial

We successfully obtained a no-cause jury verdict in a 13-day wrongful death trial. The decedent, a 59-year-old man, was admitted to the emergency room on February 15, 2019, with complaints of abdominal pain, decreased appetite, and constipation, despite the use of laxatives. The patient did not complain of any nausea, vomiting, or diarrhea. He had a significant medical history including diabetes, hypertension, prior coronary artery stenting, morbid obesity (with past gastric bypass surgery), longstanding ventral hernia, and back pain. A CT scan revealed multiple hernias and a potential closed-loop bowel obstruction, leading to a surgery consultation. Our client, an emergency general surgeon, interpreted that the patient did not have a closed loop or any significant obstruction and recommended non-surgical management. The patient was approved to have clear liquids, and had a vomiting incident shortly after, but our client was not notified. The patient was returned to NPO status, and after improving overnight, he was returned to “clears” and additional medical and renal consults were ordered. Our client did not receive any communications from the residents/nurses of any changes in the patient’s condition. On February 18, 2019, two rapid responses were called due to increased heart rate and vomiting. It is believed that the vomiting resulted in aspiration, causing sepsis, ultimately leading to the patient’s death. During the trial, the plaintiff’s sole medical expert highlighted imaging on the wrong hernia, which called into question all of his opinions in the case. We made key objections related to the expert testimony, limiting what the allegations were, and preventing new allegations from being made. After approximately two and a half hours of deliberating, the jury returned a no-cause verdict. 

Thought Leadership

The Best Defense is Already in the File: Documentation in Civil Rights Litigation

Casey Alan Coyle Joins Marshall Dennehey's PA Appellate Practice as a Shareholder in Harrisburg and Philadelphia

News

Marshall Dennehey Expands Leading Pennsylvania Appellate Practice With Addition of Shareholder Casey Coyle

Thought Leadership

New Jersey Appellate Division Affirms Exclusion of Legal Malpractice Expert as Impermissible Net Opinion

Jack Slimm and Jeremy Zacharias obtained a favorable decision on behalf of their client in a case centering on the admissibility of expert testimony in legal malpractice actions. In Martin v. Loury, the New Jersey Appellate Division affirmed the exclusion of a plaintiff's legal malpractice expert, holding that the expert's opinions on causation and damages were too speculative to support the malpractice claim. The legal malpractice action arose from an underlying employment dispute involving claims for damages stemming from the breach of an employment agreement. The plaintiff alleged that defense counsel committed malpractice during a second trial by failing to recall the plaintiff as a rebuttal witness after the employer's CEO testified. According to the plaintiff's expert, additional rebuttal testimony would have bolstered the plaintiff's damages claims and led to a more favorable result. Both the trial court and the Appellate Division rejected that theory. The courts found that the expert could not explain how the proposed rebuttal testimony would have altered the outcome of the underlying case or resulted in any additional recoverable damages. Notably, the trial judge in the underlying employment matter had already rejected the CEO's testimony as not credible and had accepted the damages analysis advanced by the plaintiff. The court had also determined that the amount of damages was not genuinely disputed. As a result, the expert's opinion that additional rebuttal testimony would have produced a better outcome was unsupported by the record and based on speculation rather than evidence. The Appellate Division agreed that neither the plaintiff nor the expert could identify any actual damages attributable to the alleged malpractice or demonstrate the required element of proximate causation. The court further upheld the trial court's application of New Jersey's net opinion doctrine, finding that the expert failed to provide the necessary "why and wherefore" supporting his conclusion that the attorney's conduct caused a compensable loss. Because the opinions rested on unquantified possibilities rather than demonstrable facts, they were inadmissible. Key Takeaway for Legal Malpractice Defendants For attorneys and firms defending legal malpractice claims, Martin v. Loury underscores the importance of closely scrutinizing an opponent's expert report on the critical elements of proximate causation and damages. The decision demonstrates that a malpractice claim cannot survive where an expert merely speculates that different litigation tactics might have produced a better result. Instead, the plaintiff must present admissible expert testimony grounded in the record that explains how the alleged attorney error probably changed the outcome of the underlying matter and resulted in measurable damages.

Thought Leadership

Ohio Supreme Court Holds That a Binding Appraisal Award May Not Be Set Aside Absent Specific Evidence of Manifest Mistake or Fraud

On July 23, 2026, the Ohio Supreme Court issued a rare opinion on the binding effect of an appraisal award in a property insurance policy.  The Court in One Church held: A binding appraisal award will not be set aside unless an error is so palpably wrong that it undermines the intent of the agreement, such as corruption or gross mistake, not a mere error of judgment—To plead a claim of mistake with particularity as required by Civ.R. 9(B), facts alleged in a complaint must constitute the elements of mistake—Allegation that additional, hidden damage was discovered after appraisal award failed to state a claim of mistake that could justify setting aside binding appraisal.  The case arose out of a claim brought by One Church against its insurer, Brotherhood Mutual Insurance Company for roof damage from a storm. Pursuant to the terms of the insurance policy, the parties agreed to submit the matter to appraisal. The two appraisers inspected the building, and both appraisers agreed that the damages were $313,271.98. The insurer paid the agreed appraised amount.  Thereafter, the insured submitted a claim for an additional $206,663.09 in damages. The insured argued that these additional damages were not discovered until after the repairs began, and that they should be permitted to submit an additional claim, even though there had already been a binding appraisal of damages. The insurer refused to pay the additional damages, and the insured sued for breach of contract and bad faith.  In the trial court, the insurer moved to dismiss for failure to state a claim, arguing that the binding appraisal award barred any further claims. The insured took the position that additional hidden damages could not be discovered until after the repairs began, and therefore there was a mutual mistake. The trial court dismissed the case on the insurer’s motion, because there was no “evidence of fraud, misfeasance, or mistake”. The Court of Appeals agreed that appraisal awards are generally binding, but noted that an appraisal award can be set aside for fraud or manifest mistake. The Court of Appeals reversed and remanded the case to the trial court, finding that the insured had pled mistake with sufficient particularity. The insurer appealed to the Ohio Supreme Court. On appeal, the Ohio Supreme Court reversed the Court of Appeals, and reinstated the trial court decision dismissing the case for failure to state a claim upon which relief can be granted. The Supreme Court found that since the insured had already demanded appraisal, and the appraisal award was binding, “something more than error of judgement, such as corruption in the arbitrator, or gross mistake” must be pled with particularity, and proven for the insured to override the appraisal award. Since the complaint did not allege fraud or manifest mistake with sufficient particularity, something more than a mere error of judgment, the complaint was insufficient to state a claim.  The complaint in this case did not challenge the appraisal award. It pled that additional damages were discovered that were not apparent when the appraisal was done. It did not specify “who discovered the damages, how they were discovered, where they were found, why they were previously hidden, or why they rise to the level of a manifest mistake that the “appraiser would have corrected...had it been called to his attention”. Id at ¶22 citing Lakewood Mfg. Co. v. Home Ins. Co. of New York, 422 F.2d 796, 798 (6th Cir. 1970). Cases deciding the effect of appraisal awards are unusual. The Ohio Supreme Court’s decision in One Church relies primarily on 19th century case law for its conclusion. This emphasizes the fact that there is minimal case law deciding the effect of binding appraisal clauses in property insurance policies, and makes this case all the more significant. A lengthy dissent was written by Justice Fisher, who would have affirmed the Court of Appeals decision reversing and remanding the case for a decision on the merits. Of course, the decision works both ways, and an insurer dissatisfied with a binding appraisal award will likewise be without further recourse absent evidence of corruption, fraud, misfeasance, or manifest mistake, which must be pled with particularity. To constitute manifest mistake, “the mistake must be of such character that the arbitrator or appraiser would have corrected it had it been called to his attention.”  Lakewood Mfg. Co. v. Home Ins. Co. of New York, 422 F.2d 796, 798 (6th Cir. 1970).  The majority opinion does not specifically identify what would have been sufficient to plead mistake with particularity, or if the insured could have amended the complaint to overcome the deficiencies. The dissent argues that this was not really a case alleging mistake, but rather a question of contract interpretation. The insured did not challenge the appraisal, but argued that the hidden damage was not part of the appraisal, and the appraisal only covered the known damages.  However, this argument did not carry the day with the majority. 

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Result

Summary Judgment Secured for Life Insurance Agent

blue facade of a hospital sign against blue sky

Result

Defense Verdict in Complex Medical Malpractice Trial