On that point, plaintiff does not dispute that, as a general rule, a plaintiff in a medical malpractice case must offer expert testimony that, to a reasonable medical probability, the alleged breach of the standard of care caused the plaintiff's injuries. See Cleland v. Wilcox, 273 Or. 883, 887-88, 543 P.2d 1032 (1975); Myers v. Dunscombe, 64 Or. App. 722, 723, 669 P.2d 388, rev den 296 Or. 236 (1983). She also does not dispute that no expert said that her tumor caused the physical symptoms she experienced.

In order to establish causation, a plaintiff must demonstrate a reasonable probability that the alleged conduct caused the alleged harm. See Joshi v. Providence Health System of Oregon Corp., 198 Or. App. 535, 545, 108 P.3d 1195 (Or. App. 2005) ("Proof of cause-in-fact `must have the quality of reasonable probability, and a mere possibility that the alleged negligence of the defendant was the . . . cause of plaintiff's injuries is not sufficient.'" (quoting Cleland v. Wilcox, 273 Or. 883, 887, 543 P.2d 1032 (1975))). Yeo has failed to do so.

Specifically, the court held that, because the plaintiff's medical expert could only testify to a possibility, and not a probability, that the defendant had caused the plaintiffs injury, the trial court should have directed a verdict for the defendant. Id. at 49; see also Cleland v. Wilcox, 273 Or 883, 887-88, 543 P2d 1032 (1975) (quoting Sims, 224 Or at 48). Applying the "reasonable probability" causation standard to the word "caused," as used in the wrongful death statute, a plaintiff in a wrongful death case must demonstrate that the defendant's negligent act or omission more likely than not brought about the death of the decedent.

James v. Carnation Co., 278 Or. 65, 69, 562 P.2d 1192 (1977). Relying on Myers v. Dunscombe, 64 Or. App. 722, 669 P.2d 388, rev den 296 Or. 236 (1983), and Cleland v. Wilcox, 273 Or. 883, 543 P.2d 1032 (1975), defendants argue that this is a case involving a complex medical issue that requires expert testimony to establish causation with reasonable probability. In Myers v. Dunscombe, supra, the plaintiff brought a dental malpractice action for nerve damage that the plaintiff allegedly suffered as the result of a negligently administered injection by the defendant's assistant.

, a plaintiff must present expert testimony showing that there is a reasonable medical probability that the injuries were caused by the defendant. See Cleland v. Wilcox, 273 Or. 883, 887 (1975) (“Where injuries complained of are of such character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science and must necessarily be determined by testimony of skilled, professional persons.” (simplified)). “Th[is] rule prevents jurors from speculating about causation in cases where that determination requires expertise beyond the knowledge and experience of an ordinary lay person.”

See Joshi v. Providence Health System of Oregon, 198 Or.App. 535, 544, 108 P.3d 1195 (2005), aff'd by 342 Or. 152, 149 P.3d 1164 (2006); Horn v. National Hospital Association, 169 Or. 654, 679, 131 P.2d 455 (1942). Causative proof “must have the quality of reasonable probability, and a mere possibility that the alleged negligence of the defendant was the cause of plaintiff's injuries is not sufficient.” Cleland v. Wilcox, 273 Ore. 883, 887, 543 P.2d 1032 (1975); Sims v. Dixon, 224 Ore. 45, 48, 355 P.2d 478 (1960); see also Henderson v. U. P. R. R. Co., 189 Or. 145, 162, 219 P.2d 170 (1950) (“Without competent medical testimony that the blow which the plaintiff received was the probable cause of the gangrene and resulting amputation, there could be no case sufficient to go to the jury on that question.”)

Under Oregon law, in most instances, liability for medical malpractice depends on expert testimony to prove a violation of the standard of care. See Chownard v. Health Ventures, 179 Or. App. 507, 511-12, 39 P.3d 951 (2002); see also Cleland v. Wilcox, 273 Or. 883, 887, 543 P.2d 1032 (1975) ("[W]here injuries complained of are of such character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science and must necessarily be determined by testimony of skilled, professional persons." (quotations and citation omitted)).

When injuries are complex and not a simple "cause and effect" correlation, expert testimony is required: "[i]t is, of course, the settled rule that where injuries complained of are of such character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science and must necessarily be determined by testimony of skilled, professional persons." Cleland v. Wilcox, 273 Or. 883, 887, 543 P.2d 1032 (Or. 1975) (citations omitted); see Chouinard v. Health Ventures, 179 Or. App. 507, 512, 39 P.3d 951 (Or.Ct.App. 2002). "If the issue turns upon some fact beyond the ken of laymen, expert testimony must be produced."

The Oregon Supreme Court has long recognized the settled rule that in instances of injuries that are "of such character as to require skilled and professional persons to determine the cause and extent thereof, the question is one of science and must necessarily be determined by testimony of skilled, professional persons," and that if the "issue turns upon some fact beyond the ken of lay[persons], expert testimony must be produced." Uris v. State Comp. Dept., 427 P.2d 753, 755 (Or. 1967) (internal quotations and citations omitted); see also Cleland v. Wilcox, 543 P.2d 1032, 1034 (Or. 1975) (a jury should not be permitted to resolve causation questions arising from complicated injury allegations without expert medical testimony). Plaintiff fails to establish what the reasonable professional practice for blood draws is in the Portland community, a question that falls outside the knowledge of a typical jury.

"It is apparent from the evidence presented by the plaintiff in this case, examined in light of the principles stated in Uris v. Compensation Department, supra, that no medical testimony is necessary * * *." See also Barrett v. Coast Range Plywood, 294 Or. 641, 645, 661 P.2d 926 (1983) (in workers' compensation claim, whether rule regarding necessity for expert medical testimony is to be applied depends on whether medical question presented is "uncomplicated"); Cleland v. Wilcox, 273 Or. 883, 543 P.2d 1032 (1975) (where physician's evidence showed plaintiff's injury was not an "uncomplicated situation," rule stated in Uris required expert medical testimony); Austin v. Sisters of Charity, 256 Or. 179, 183, 470 P.2d 939 (1970) (where features of case met criteria set out in Uris, jury could decide causation of injury without expert testimony). Claimant's argument centered on the meaning and application of the term "uncomplicated" and related terms, as applied to the medical "situations" of workers' compensation claimants.