## Facts

- Jeff and Lynn Easum owned and operated a family dairy in Wyoming.
- Clay Miller, doing business as Prime Power & Communications, LLC (Prime Power), performed electrical work that included placing or replacing an electrical transformer near the dairy.
- After Prime Power’s work, a neutral line was left unconnected, causing stray voltage in and around the dairy facilities.
- Jeff Easum experienced numerous electrical shocks while working at the dairy during the period of stray voltage.
- After the neutral line was properly connected, the stray voltage condition and shocks stopped, but Jeff’s symptoms continued.
- Jeff was later diagnosed with reflex sympathetic dystrophy (RSD), which he attributed to electrical injury from repeated low-level shocks.
- The Easums sued Miller/Prime Power for property damage and personal injuries. The property-damage portion was resolved by settlement.
- On the remaining personal-injury claims, the Easums offered causation testimony from Jeff’s treating neurologist, Dr. Hooshang Hooshmand.
- Dr. Hooshmand evaluated Jeff through extensive diagnostic testing over approximately 14 days and used differential diagnosis to rule out other possible causes before concluding that the repeated low-level electrical shocks caused Jeff’s RSD.
- Dr. Hooshmand also relied on his clinical experience, including treating other dairy farmers exposed to stray voltage, but his specific low-level-electricity theory was not supported by peer-reviewed publications and could not readily be tested through controlled human experimentation.
- Miller/Prime Power moved for summary judgment, arguing Dr. Hooshmand’s causation opinion was unreliable under Daubert and Wyoming’s decision in Bunting v. Jamieson and therefore inadmissible; without it, the Easums could not prove causation.
- The district court excluded the causation opinion as unreliable and granted summary judgment against the Easums on the personal-injury claims.

## Issues

1. Whether a treating physician’s causation opinion based on a properly performed differential diagnosis is sufficiently reliable under Daubert and Bunting to be admitted, even when peer-reviewed studies on the specific causal mechanism are limited or unavailable.
2. Whether, with that opinion excluded, the district court properly granted summary judgment on the ground that the Easums could not establish causation.

## Decision

- The Wyoming Supreme Court reversed the summary judgment and remanded for trial.
- The court held the district court abused its discretion by excluding Dr. Hooshmand’s differential-diagnosis-based causation testimony as unreliable.
- The court concluded the district court applied an overly strict view of Daubert/Bunting by treating publication, peer review, or experimental verification as a required condition for admissibility in this clinical causation setting.
- Because the causation testimony should have been admitted, a genuine dispute of material fact existed on causation, making summary judgment improper.

## Legal Principles

- Under Wyoming Rule of Evidence 702, as applied through Daubert and Bunting, the trial court acts as a gatekeeper to ensure expert testimony is relevant and based on reliable methods; the court does not decide which side’s experts are more convincing when the methods are sound.
- Differential diagnosis (differential etiology) is a recognized clinical method for determining the cause of a patient’s condition when it involves (1) collecting history and clinical data, (2) identifying plausible causes, and (3) systematically ruling out alternatives to reach a reasoned conclusion.
- Daubert’s considerations (testability, peer review/publication, known or potential error rate, and general acceptance) are flexible guides rather than a checklist of mandatory requirements; in some medical contexts, controlled human testing may be impossible or unethical.
- The absence of peer-reviewed literature on a specific mechanism does not automatically make a treating physician’s causation opinion inadmissible when the physician relies on examination, diagnostic testing, clinical reasoning, and elimination of alternatives.
- Challenges to the factual basis for an otherwise reliable differential diagnosis ordinarily affect weight and credibility for the factfinder, not admissibility.
- When admissible expert testimony would allow a reasonable jury to find causation, summary judgment should not be used to resolve competing medical opinions.

## Conclusion

Easum v. Miller held that Dr. Hooshmand’s treating-physician causation opinion, reached through extensive testing and differential diagnosis, met Wyoming’s Daubert/Bunting reliability standard despite limited peer-reviewed support for the precise low-level-electricity mechanism; excluding that testimony and then granting summary judgment was an abuse of discretion, so the case was reversed and remanded for trial.


Easum v. Miller, 92 P.3d 794, 2004 WY 73 (2004)