Uriell v. Regents of University of California, 234 Cal. App. 4th 735

In August 2007 Barbara Kastan (strong family history of breast cancer) presented to UCSD with a palpable 2 cm left-breast mass; mammogram and ultrasound were read as reassuring (dense breast; simple cysts). Dr. Blair did not order MRI or biopsy and told patient she did not have cancer.
By January–May 2009 Kastan had progressive breast and systemic signs; biopsy in May 2009 diagnosed breast cancer that was advanced; she died December 8, 2010.
Plaintiffs (husband and children) sued the Regents for wrongful death, alleging delayed diagnosis caused earlier death. Plaintiffs’ oncology expert (Dr. Brouillard) testified to a reasonable degree of medical probability that earlier diagnosis/treatment in 2007 would have prolonged Kastan’s life by about 10 years.
Defense experts testified either that cancer was already metastatic in 2007 and earlier treatment would not likely extend life beyond a few years, or that microscopic cancer may have been present. The trial court denied nonsuit; jury found UCSD negligent and its negligence a substantial factor in causing harm. Judgment for plaintiffs.
On appeal Regents argued (1) Dr. Brouillard’s survival opinion lacked adequate foundation and was speculative, and (2) the court erred by giving standard substantial-factor causation instructions (CACI 430/431) without a special instruction requiring causation be shown to a "reasonable medical probability." The Court of Appeal affirmed.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Admissibility/foundation of expert's opinion that earlier diagnosis would have extended life ~10 years	Brouillard relied on patient records, tumour biology (ER+, HER2-), response to later treatment, and his clinical experience to conclude earlier treatment would likely have produced long-term survival	Regents: opinion speculative, based on family history and insufficient foundation to show >50% probability of 10-year survival; thus nonsuit/new trial warranted	Admissibility proper. Brouillard gave a reasoned, experience- and record-based opinion; trial court did not abuse discretion admitting it and denying nonsuit/new trial.
Jury instructions on causation—whether a special "reasonable medical probability" instruction was required	Plaintiffs: standard negligence/"substantial factor" instructions suffice; medical-probability concerns are addressed by expert testimony and burden of proof	Regents: Jones and related cases require instruction emphasizing causation must be proven to a reasonable medical probability (not mere possibility)	No error. Standard CACI substantial-factor instructions plus preponderance burden were adequate; Jones and similar cases address evidentiary sufficiency, not a different jury instruction. CACI 431 on concurrent causes was appropriate.

Sargon Enterprises, Inc. v. University of Southern California, 55 Cal.4th 747 (gatekeeper standard for expert admissibility; focus on methodology not conclusions)
Jones v. Ortho Pharmaceutical Corp., 163 Cal.App.3d 396 (expert must show causation as a reasonable medical probability; distinguishes possibility from probability)
Dumas v. Cooney, 235 Cal.App.3d 1583 (lost-chance analysis where only a 30% survival chance was shown; causation not established)
Bromme v. Pavitt, 5 Cal.App.4th 1487 (nonsuit proper where experts agreed survival chance <50% so negligence was not a substantial factor)
Espinosa v. Little Co. of Mary Hospital, 31 Cal.App.4th 1304 (concurrent substantial causes — plaintiff need not apportion damages among multiple substantial causes)
Rutherford v. Owens-Illinois, Inc., 16 Cal.4th 953 (substantial-factor causation standard described)
Bockrath v. Aldrich Chemical Co., 21 Cal.4th 71 (even minor forces can be causes; infinitesimal/theoretical forces are not substantial factors)
Flowers v. Torrance Memorial Hospital Medical Center, 8 Cal.4th 992 (medical malpractice remains negligence; core elements including causation apply)