“Likely” Is Not “Reasonably Certain”: Forfeiture of Obvious-Causation and Strict Medical-Certainty Proof of Causation in Pennsylvania Personal-Injury Product Cases

1. Introduction

In Joseph Riad v. Porsche Cars North America Inc (3d Cir. Jan. 30, 2026) (non-precedential), the Third Circuit affirmed summary judgment against Joseph Edward Riad, who alleged he suffered respiratory injuries after inhaling fumes that entered the cabin of his 2004 Porsche Cayenne Turbo during an engine-coolant leak. Riad sued Porsche Cars North America, Inc. (the vehicle’s exclusive domestic importer) under Pennsylvania law, asserting (i) strict liability design defect and (ii) negligent failure to warn, and sought over $5 million.

The appeal centered on a single dispositive element: causation. Pennsylvania recognizes two pathways to prove causation in personal-injury cases: (1) an “obvious causal relationship” or (2) “unequivocal medical testimony” expressed to a “reasonable degree of medical certainty.” The Third Circuit held Riad failed under both—one by forfeiture, the other by inadequate expert proof.

2. Summary of the Opinion

  • Obvious causal relationship theory forfeited: Riad did not develop that argument in the District Court, so he could not revive it on appeal.
  • Expert causation opinion insufficient: Riad’s expert expressed a reasonable degree of medical certainty as to Riad’s current pulmonary pathology, but described causation only as “likely” and elsewhere as merely “possible.” That does not satisfy Pennsylvania’s requirement of causation testimony to a reasonable degree of medical certainty.
  • Context cannot cure tentativeness here: Although some cases allow an expert’s certainty to be assessed in context, the broader record here was “even more tentative,” including reliance on self-reporting, lack of testing, and a remote consultation.
  • Daubert and reconsideration rulings affirmed: The District Court did not rely on the defense expert to grant summary judgment, so denying Riad’s Daubert motion as moot was not an abuse of discretion; reconsideration was properly denied as well.

3. Analysis

A. Precedents Cited

1) Causation as an essential element; summary judgment framework

  • Mellon v. Barre-Nat'l Drug Co., 636 A.2d 187, 191 (Pa. Super. Ct. 1993): Cited for the baseline rule that causation is essential in both products liability and negligence. This anchors the conclusion that failure on causation alone warrants judgment for the defendant.
  • Mall Chevrolet, Inc. v. Gen. Motors LLC, 99 F.4th 622, 630 (3d Cir. 2024) and Celotex Corp. v. Catrett, 477 U.S. 317, 322 (1986): Used to explain the “Celotex approach” to summary judgment— where the nonmovant bears the burden at trial and fails to make a sufficient evidentiary showing on an essential element, summary judgment is appropriate. The Third Circuit applied this directly: absent admissible proof of causation, Riad could not proceed.

2) Pennsylvania’s two-track causation doctrine (obvious relationship vs. medical certainty)

  • Florig v. Sears, Roebuck & Co., 130 A.2d 445, 447 (Pa. 1957): Supplies the core dichotomy: when causation is not obvious, it must be proven by “unequivocal medical testimony.”
  • Montgomery v. Bazaz-Sehgal, 798 A.2d 742, 750-52 (Pa. 2002): Reinforces and elaborates on the “obvious causal relationship” pathway. The Third Circuit cited it to show the doctrine exists, but did not reach its merits because Riad forfeited the argument below.
  • Mitzelfelt v. Kamrin, 584 A.2d 888, 892 (Pa. 1990): Defines “unequivocal medical testimony” as an opinion expressed to a “reasonable degree of medical certainty.” The court used this standard to measure (and reject) Riad’s expert causation opinion.
  • McMahon v. Young, 276 A.2d 534, 535 (Pa. 1971): Cited for the policy rationale: if the medical expert cannot reach sufficient certainty, the jury lacks a reliable basis for a legal causation finding. This supports strict policing of probabilistic phrasing.
  • In re Paoli R.R. Yard PCB Litig., 35 F.3d 717, 750-52 (3d Cir. 1994): Confirms that Pennsylvania’s “reasonable degree of medical certainty” requirement governs in federal court (including diversity cases). That forecloses any argument that federal evidentiary practice relaxes the state standard.

3) Forfeiture on appeal

  • FTC v. AbbVie Inc., 976 F.3d 327, 380 (3d Cir. 2020): Provides the appellate principle applied here: arguments not timely raised in the district court are forfeited on appeal. The Third Circuit used this to dispose of Riad’s “obvious causal relationship” theory.

4) What language fails the “medical certainty” test

  • Eaddy v. Hamaty, 694 A.2d 639, 642 (Pa. Super. Ct. 1997) (quoting Kravinsky v. Glover, 396 A.2d 1349, 1356 (Pa. Super. Ct. 1979)): Cited for the strictness of the rule: even “very highly probable” may fail if the testimony does not reach the required certainty formulation. This precedent directly undercuts Riad’s reliance on “likely.”
  • Albert v. Alter, 381 A.2d 459, 469-72 (Pa. Super. Ct. 1977): Used to show that testimony describing temporal sequence (symptoms arising after an event) does not automatically equal a causation opinion to a reasonable degree of medical certainty. The Third Circuit analogized that Riad’s expert was certain about onset/presence of pathology, not certain about cause.

5) “Context” argument—sometimes permitted, but not on these facts

  • Commonwealth v. Spotz, 756 A.2d 1139, 1160-61 (Pa. 2000): Cited for the proposition that courts may assess an expert’s statements in the context of the entire record. The Third Circuit acknowledged the method but found it unhelpful to Riad because the broader record made causation less certain, not more.

6) Daubert posture

  • Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993): Mentioned because Riad sought to exclude the defense causation expert. The Third Circuit affirmed denial as moot because summary judgment was granted without reliance on the defense expert.

7) Related procedural backdrop

  • Riad v. Porsche Cars N. Am., Inc., 657 F. Supp. 3d 695, 708 (E.D. Pa. 2023): The earlier decision dismissing Porsche AG for lack of personal jurisdiction contextualizes that the case proceeded only against the importer.

B. Legal Reasoning

  1. Issue narrowing to causation: The panel treated causation as dispositive. Under Pennsylvania law (per Mellon), both strict liability personal-injury claims and negligence personal-injury claims require causation. Under Celotex and Mall Chevrolet, the absence of admissible evidence on an essential element ends the case at summary judgment.
  2. Forfeiture bars the “obvious causal relationship” route: Because Riad did not develop that theory in district court, FTC v. AbbVie Inc. foreclosed it on appeal. The court’s handling underscores a practical point: Pennsylvania’s “obvious causation” doctrine is not a fallback available for the first time on appeal.
  3. Medical certainty must attach to causation, not merely diagnosis: The expert reported certainty that Riad suffered pulmonary pathology not present before the incident, but addressed causation in probabilistic terms (“likely”) and elsewhere as merely “possible.” The panel treated that distinction as fatal: Pennsylvania requires the expert to reach a reasonable degree of medical certainty that the exposure caused the injury, not simply that an injury exists. The court’s reliance on Eaddy, Kravinsky, and Albert reflects a consistent doctrinal line: words signaling speculation or possibility do not meet the standard.
  4. Context cannot elevate speculation into certainty when the record undermines reliability: Invoking Commonwealth v. Spotz, Riad argued the whole record could supply the needed certainty. The Third Circuit rejected that move because surrounding evidence accentuated uncertainty—remote evaluation, missing testing, and heavy reliance on self-report. In other words, “context” is not a magic wand; it can confirm certainty, but it cannot manufacture it where the expert and evidentiary foundation remain tentative.
  5. Daubert and reconsideration are non-dispositive once plaintiff’s proof fails: Because the defense expert was not used to grant summary judgment, exclusion of that expert could not cure plaintiff’s lack of causation evidence. The court therefore found no abuse of discretion in denying the Daubert motion as moot and denying reconsideration.

C. Impact

Although designated “NOT PRECEDENTIAL,” the decision is a clear cautionary application of Pennsylvania causation law in federal court and will likely be cited for its straightforward treatment of two recurring litigation failures.

  • Litigation strategy and preservation: Plaintiffs must squarely brief and develop the “obvious causal relationship” theory at the trial level if they intend to rely on it. Otherwise, they risk forfeiture under FTC v. AbbVie Inc..
  • Expert drafting and deposition discipline: Expert reports and deposition testimony must explicitly tie causation to a “reasonable degree of medical certainty,” not merely state that causation is “likely,” “possible,” or one of several “possibilities.” This opinion shows courts will parse language with precision, especially at summary judgment.
  • Foundation matters: The court’s emphasis on lack of testing, remote consultation, and reliance on self-reporting signals that even if “magic words” appear somewhere, a weak methodological foundation can make “context” arguments harder to sustain.
  • Daubert motions are not a substitute for affirmative proof: Excluding a defense expert does not fill the gap when the plaintiff’s own proof fails on causation.

4. Complex Concepts Simplified

“Obvious causal relationship”
A narrow category where lay jurors can infer cause-and-effect without medical experts—e.g., a clearly immediate and direct injury. If the relationship is not obvious, Pennsylvania requires expert medical proof.
“Unequivocal medical testimony” / “reasonable degree of medical certainty”
A requirement that the expert’s causation opinion be stated with sufficient professional certainty—not mere possibility. Language such as “possible” or “likely” (as used here) may be treated as too speculative to let a jury find causation.
Summary judgment (Celotex framework)
A case can be decided without trial if the party who must prove an element (here, causation) lacks evidence that could allow a reasonable jury to find in its favor.
Forfeiture on appeal
Appellate courts generally will not consider arguments not properly raised in the trial court. Preservation requires timely and developed presentation below.
Daubert motion
A challenge to whether an expert’s testimony is reliable and admissible. But excluding the opposing expert does not prove your own case.

5. Conclusion

The Third Circuit affirmed summary judgment because Riad failed to produce legally sufficient evidence of causation under Pennsylvania law. His “obvious causal relationship” theory was forfeited by not being developed in the District Court, and his expert’s causation opinion—framed as merely “likely” and sometimes “possible”— did not meet the “reasonable degree of medical certainty” requirement recognized in Florig v. Sears, Roebuck & Co. and Mitzelfelt v. Kamrin. Even viewing testimony in context (per Commonwealth v. Spotz) could not cure the record’s overall tentativeness.

The opinion’s practical significance is its crisp reminder: in Pennsylvania personal-injury product cases in federal court, causation must be preserved, proven, and stated with the required certainty— and “likely” is not enough.