## Facts

- Bob T. Moore, an Ashland Chemical terminal manager in Texas, was directed to help clean a spill caused by a tank truck hose failure.
- The spill released a large, unidentified mixture of chemical vapors that included toluene.
- Moore alleged that an acute exposure during the cleanup caused reactive airways dysfunction syndrome (RADS) or a chronic lung disease.
- Moore and his wife sued Ashland for negligence, alleging Ashland required or allowed unsafe exposure that caused Moore’s respiratory condition.
- Moore was treated by physicians including Dr. Daniel Jenkins and Dr. Antonio Alvarez, who attributed Moore’s condition to the chemical exposure.

## Issues

1. Whether the district court abused its discretion under Federal Rule of Evidence 702 and *Daubert* by excluding Dr. Jenkins’s treating-physician causation opinion as unreliable.
2. Whether excluding that causation testimony affected the plaintiffs’ substantial rights, requiring a new trial.

## Decision

- The Fifth Circuit panel held the district court erred by excluding Dr. Jenkins’s causation testimony.
- The panel concluded Dr. Jenkins’s opinion was based on reliable clinical medical methodology and was relevant to the central causation question.
- The panel held the evidentiary error was not harmless because it likely influenced the jury’s proximate-cause finding.
- The panel vacated the judgment for Ashland and remanded for a new trial.

## Legal Principles

- Under Rule 702 and *Daubert*, medical causation opinions may be reliable when grounded in accepted clinical methods, including patient history, physical examination, diagnostic testing, temporal association, and differential diagnosis.
- *Daubert* reliability factors (testing, peer review, error rate, and general acceptance) are flexible and should not be applied as mandatory requirements in every context.
- Lack of precise quantitative exposure data (e.g., exact dose or mixture composition) does not automatically render a clinical causation opinion inadmissible; such limits may go to weight rather than admissibility when the clinical reasoning is otherwise sound.
- Excluding admissible expert testimony on a central element like causation can be reversible error when it likely affects the verdict, even if another expert offers similar testimony.

## Conclusion

The panel ruled that a treating physician’s causation testimony based on standard clinical evaluation and differential diagnosis met Rule 702 and *Daubert* reliability requirements, and that excluding it was prejudicial, warranting vacatur and a new trial.


Moore v. Ashland Chem., Inc., 126 F.3d 679 (5th Cir. 1997)