A Philadelphia jury handed ExxonMobil a clear defense win on Oct. 13, rejecting claims that the company’s benzene-containing gasoline was defectively designed and caused a man’s leukemia. Jurors also found the product lacked adequate benzene warnings, yet they refused allegations that ExxonMobil intentionally hid the chemical’s dangers.
The verdict came in the suit filed by Leon and Ruth Mazza and landed just days before a Pennsylvania appeals court left a separate, massive plaintiff award against the company intact on procedural grounds. For oil companies facing a wave of product and climate suits, the split outcomes show how fact questions, warning claims, and appellate rules can cut in different directions at once.
The Daily Caller reported that the Mazzas sued in July 2023 after Leon Mazza’s 2022 leukemia diagnosis. Their filing named ExxonMobil along with Shell, Chevron, BP, U.S. Steel and others. Philadelphia-based Locks Law Firm represented the plaintiffs, the same firm tied to an earlier Philadelphia gasoline case that produced a nine-figure verdict.
Jurors found ExxonMobil’s benzene-containing gasoline was not defectively designed. They also concluded the company did not intentionally conceal benzene’s dangers. At the same time, they found the gasoline lacked an adequate benzene warning.
Plaintiffs argued there is no safe level of benzene exposure and pointed to the International Agency for Research on Cancer’s reclassification of gasoline as carcinogenic to humans. The jury was not persuaded that the products caused Mazza’s leukemia.
Energy analyst David Blackmon framed the result as a facts-over-feelings outcome in a high-stakes “big oil” trial.
"The verdict in the Mazza case shows that juries still rule on facts rather than emotions when a ‘big oil’ defendant makes its case."
Blackmon also told the Daily Caller News Foundation the claims against Exxon “were specious on their face.” He said there is “no valid science supporting such a claim and the jury figured it out despite the best efforts of plaintiff lawyers to cloud the facts.”
Leon Mazza’s alleged exposures included work at a Wyndmoor Exxon station, an auto body shop and landscaping businesses, plus personal use of benzene-containing products in a drag-racing hobby. An embedded summary of the case described landscaping-related exposures spanning 1970 to 2020. He was diagnosed in 2022.
Benzene is a known human carcinogen linked to leukemia, according to the National Cancer Institute. The Centers for Disease Control and Prevention states that health effects from chemical exposure depend on the amount and duration of exposure. Those public-health points framed the dispute. They did not dictate the jury’s product-defect and causation answers.
ExxonMobil did not immediately respond to a Daily Caller News Foundation request for comment after the verdict.
The Mazza defense win stood in sharp contrast to another Philadelphia gasoline case. In May 2024, a jury awarded Paul Gill $725 million after finding Mobil Oil negligently sold defective gasoline containing benzene. Diane Gill received $500,000.
On Oct. 15, 2026, the Pennsylvania Superior Court upheld the $725.5 million Gill verdict. The appellate outcome turned heavily on issue preservation, not a full re-weighing of the disputed science.
Judge Deborah Kunselman wrote that Exxon’s appeal faltered because key arguments never made it into the trial record in usable form.
"Exxon failed to preserve most of its arguments regarding sufficient proof of causation, and that waiver renders its only preserved argument moot."
Blackmon said the ruling confirming the huge award rested on procedural grounds rather than the facts of the case, leaving room for further appeals. Locks Law Firm’s presence in both the Mazza and Gill matters sharpened the industry’s interest in how different juries, and then different courts, treated overlapping benzene theories.
The Mazza and Gill cases sit inside a wider docket. Earlier in October, a New York appeals court rejected New York City’s lawsuit against ExxonMobil, Shell and BP. That court upheld dismissal of claims accusing the companies of misleading consumers about the environmental benefits of their products.
On Oct. 5, 2026, the U.S. Supreme Court heard arguments over whether state-law claims can proceed against energy companies for alleged climate-related harms. The matter involves Colorado localities and Suncor Energy, with ExxonMobil in the mix.
O.H. Skinner, executive director of the Alliance for Consumers, previously warned the Daily Caller News Foundation about the broader pattern in related litigation.
"Without the Court stepping in, progressive activists and their trial lawyer allies will continue to advance their woke lawfare campaign across the country."
In Washington state, a wrongful death suit tied to the 2021 Pacific Northwest heat wave alleges fossil fuel producers contributed to conditions that killed Juliana Leon. A judge rejected defendants’ motion to dismiss in July. Companies sought appellate review. By September, BP, Chevron, Shell and other defendants were out of the case, leaving ExxonMobil entities and TransMontaigne Partners facing the remaining claims.
Product-defect and climate theories are not the only pressure point. Locks Law Firm and Berger Montague filed a class action over an alleged gasoline leak at a Pennsylvania storage facility, the Chelsea Tank Farm in Aston. The suit accuses Monroe Energy and a subsidiary of contaminating properties and groundwater through an alleged 378,000-gallon release.
That filing targets storage and release conduct rather than a consumer cancer-design theory. It still adds to the volume of high-dollar gasoline litigation surrounding refiners, marketers and related firms in Pennsylvania.
Authorities and the public record described in the reporting have not detailed a full formal docket caption for the Mazza case, nor the exact damages picture left after the Oct. 13 findings. Investigators and courts in related matters will need to determine how warning claims, causation proof and issue-preservation rules interact when plaintiffs try to convert benzene exposure narratives into nuclear verdicts.
No public results in the seed reporting settle whether other named Mazza defendants, including Shell, Chevron, BP and U.S. Steel, faced the same jury findings as ExxonMobil. ExxonMobil’s substantive response beyond the lack of an immediate comment also remains outside the public statements captured in that coverage.
On the Gill track, the Superior Court’s waiver-centered opinion keeps the focus on what a defendant must raise at trial to attack causation later. Blackmon’s read is that procedural defeat is not the same as scientific validation of the underlying claim, and that further appellate steps remain possible.
One Philadelphia jury rejected the core defective-design and concealment attack on ExxonMobil gasoline in a leukemia case. Another Philadelphia jury had already delivered a $725.5 million plaintiff award in a related benzene-gasoline theory, and an intermediate appeals court left that award standing because most causation challenges were not preserved.
Business groups had warned after Gill-type “nuclear verdicts” that such awards raise costs for everyone. Blackmon’s October 19 social thread on the Mazza result underscored the contrast, including a juror’s later blog description from the Gill matter about the “best feeling ever” of watching Exxon lawyers look as if they “were going to puke.” The Mazza jury’s refusal to adopt the “gasoline causes cancer” causation theory, as summarized in that thread, undercuts any claim that every benzene case ends the same way.
Across New York consumer-messaging claims, Supreme Court arguments on state-law climate suits, the Washington heat-wave death case and the Aston tank-farm class action, energy defendants are fighting multiple doctrines at once. Some fights turn on design and warnings. Others turn on causation, preemption, standing or issue preservation.
The practical stakes are straightforward. When juries demand proof tying a specific product defect to a specific disease, plaintiffs face a hard wall. When defendants lose issue-preservation fights, enormous judgments can survive even if the science remains contested. Warning findings without design liability create a third path that still exposes companies to compliance and labeling risk without establishing the broader causation story plaintiffs want.
Courts that insist on preserved arguments, proven causation and disciplined product claims protect both injured parties who can meet the burden and the rule of law against sprawling pressure campaigns. Juries that separate real proof from narrative momentum do the same work in real time.
