## Facts

- Fencil Urethane Systems, Inc. applied an epoxy primer inside a warehouse.
- Duane Langness later worked in the warehouse and claimed he inhaled residual chemical vapors from the primer.
- Langness alleged the exposure caused serious respiratory injury, including Reactive Airways Dysfunction Syndrome (RADS).
- To prove medical causation and damages, Langness offered testimony from his treating physician, Dr. Alan Buck.
- The trial court excluded or substantially limited Dr. Buck’s testimony on diagnosis and causation.
- The case went to the jury with reduced expert evidence on causation, and the jury returned a verdict for Fencil; judgment was entered dismissing Langness’s claims.

## Issues

1. Whether the trial court abused its discretion by excluding or limiting the treating physician’s expert opinions on diagnosis and medical causation.
2. Whether the exclusion was prejudicial such that it affected Langness’s substantial rights and required reversal and a new trial.

## Decision

- The Supreme Court of North Dakota held the trial court abused its discretion by excluding or sharply curtailing Dr. Buck’s diagnosis and causation testimony.
- The court ruled the error was prejudicial because medical causation was central and outside ordinary lay knowledge.
- The judgment for Fencil was reversed, and the case was remanded for a new trial.

## Legal Principles

- Expert testimony is admissible when a qualified expert’s specialized knowledge will assist the fact-finder and the opinion is relevant and supported by a reliable foundation.
- A treating physician may testify to medical causation when the opinion is grounded in accepted medical methods, including examination, patient history, review of records, and differential diagnosis.
- Objections that an expert’s conclusions are weak, uncertain, or contestable generally go to weight and credibility for the jury, not admissibility, when the methodology is sound.
- Excluding central expert causation evidence in a case turning on complex medical causation can be reversible error when it likely affected the verdict.

## Conclusion

Because the case depended on expert medical causation proof and the treating physician’s method-based causation testimony should have been admitted, the improper exclusion prejudiced Langness and required reversal and remand for a new trial.


Langness v. Fencil Urethane Sys., Inc., 667 N.W.2d 596 (N.D. 2003)