Ronald G. Perkins v. Darcy J. Hansen, 79 A.3d 342

Margie Perkins suffered progressive liver failure and died on June 6, 2007; she was placed on the UNOS transplant waitlist as status one after admission to Georgetown University Hospital on May 23, 2007.
Between May 23 and her death there were 44 livers offered but deemed unsuitable; one scheduled transplant on June 3 failed due to ABO incompatibility.
Ronald Perkins sued his wife’s treating physicians for malpractice, alleging delay in recognizing her liver failure and failure to transfer her earlier to a transplant center (between May 12–14) cost her a transplant and life.
Plaintiff proffered Dr. Esteban Mezey as an expert to testify causation and loss of chance—based on his extensive hepatology/transplant experience—that earlier admission to a transplant center would likely have yielded a transplant and survival.
Defendants objected because Dr. Mezey did not review UNOS region-two statistics (mean/median wait times) for the relevant period; the trial court excluded his causation testimony, plaintiff conceded lack of causation proof, and the court granted a directed verdict for defendants.
The D.C. Court of Appeals reversed, holding the trial court abused its discretion in excluding Mezey’s testimony and remanded for a new trial.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility of expert causation testimony	Mezey’s training and long clinical transplant experience provide adequate foundation for causation opinion	Expert must use available UNOS data for region two; without it opinion is conjecture	Admission denied below was error; experience alone can provide admissible foundation (reversed)
Need to rely on UNOS mean/median wait-time data	UNOS data not required for admissibility; missing data affects weight, not admissibility	Expert’s lack of region-specific UNOS data leaves a foundational gap	Court rejected mandatory-data rule; UNOS data is probative but not prerequisite to admit testimony
Requirement to testify that a specific surgeon would accept a liver	Plaintiff need not prove absolute certainty that a surgeon would accept a particular organ	Trial court required such specificity to establish causation	Court held law does not require expert to be personally certain; specificity goes to weight, not admissibility
Loss-of-chance theory applicability	Mezey can testify that eleven-day delay caused loss of opportunity to obtain transplant	Mezey lacked sufficient foundation for loss-of-chance opinion without data	Court allowed loss-of-chance testimony based on Mezey’s experience; exclusion was error

Snyder v. George Washington Univ., 890 A.2d 237 (D.C. 2006) (elements of malpractice and rejection of rule excluding expert testimony based solely on experience)
Derzavis v. Bepko, 766 A.2d 514 (D.C. 2000) (expert causation must show more likely-than-not causation standard)
Dyas v. United States, 376 A.2d 827 (D.C. 1977) (factors governing expert testimony admissibility)
Robinson v. United States, 50 A.3d 508 (D.C. 2012) (degree of expert certainty affects weight not admissibility)
Psychiatric Inst. of Washington v. Allen, 509 A.2d 619 (D.C. 1986) (expert need not be personally certain that plaintiff would have avoided injury but-for negligence)
Grant v. American Nat’l Red Cross, 745 A.2d 316 (D.C. 2000) (discussing loss-of-chance doctrine applicability)