Standard of Care Without a Named Source: The Med-Mal Daubert Killer (Rivera Rodriguez v. Hospital San Cristobal)

By John Mahoney · Founder, MedLegal AI · May 2, 2026

In January 2024, the First Circuit affirmed exclusion of the plaintiff's medical expert in Rivera Rodriguez v. Hospital San Cristobal. The expert had opined that the hospital's diabetic and post-surgical care fell below the standard. He never said which standard. He never named a guideline, a society statement, an institutional protocol, or a peer-reviewed standard-of-care article. He just said the care was below standard.

The First Circuit affirmed exclusion. Summary judgment for the hospital was affirmed. The case ended.

If you are a plaintiff med-mal attorney whose expert reports follow a "the care fell below the standard of care" template, Rivera Rodriguez is the case the defense bar is going to hand to the gatekeeper in your next motion.

What Happened in Rivera Rodriguez

The decedent was a hospital patient receiving diabetic and post-surgical care. The plaintiffs alleged the hospital's care fell below the applicable standard and that the deviation caused the death. They retained a medical expert. The expert wrote a report.

The First Circuit affirmed the district court's exclusion of the expert and rejected the argument that the district court was required to hold a Daubert hearing before excluding. Two interlocking findings drove the result:

1. The report did not articulate the specific standard of care. It used the phrase "standard of care" — and named the disease and the procedure — but it never identified a published or institutional source for the standard the expert claimed was applicable. There was no ADA guideline cited, no JCAHO standard, no nursing-society statement, no internal hospital protocol. Just the conclusory phrase.
2. The report did not explain how staff deviated. With no specific standard articulated, there was no reference point against which a deviation could be measured. The court characterized this as a fit problem — the testimony did not actually fit the issue the jury would have to decide.

The First Circuit affirmed exclusion under Rule 702, and held that the district court was not obligated to hold a Daubert hearing first. The exclusion was on the papers.

Why It Matters for Plaintiff Attorneys

Med-mal cases live or die on the standard-of-care opinion. Rivera Rodriguez is a clean illustration that the standard-of-care opinion now needs much more than the conclusory framing many expert reports still use.

The pattern is not isolated to the First Circuit. In Donnelly v. Our Lady of Lourdes Medical Center (N.J. App. Div. 2024), the appellate court affirmed dismissal against the defendant surgeon because the standard-of-care expert's report did not contain any opinion that the surgeon's care was a substantial cause of the decedent's death — only that it was a deviation from standard. New Jersey calls this the "net opinion" doctrine; federal courts call it fit; the gravamen is identical. Breach without proximate cause — or breach without a named standard — is structurally defective.

There are two distinct failure modes here, and both are fatal:

• No named standard. Rivera Rodriguez. The expert says "standard of care" without naming what that standard is.
• No substantial-factor causation. Donnelly. The expert says care was below standard but does not state, with the operative legal language, that the breach was a substantial cause of the harm.

Either failure mode by itself ends the case. Together, they make a Daubert motion almost mechanical to write.

The deeper reason these reports fail is that the standard-of-care opinion has been treated for decades as the "easy" part of an expert report — the part where the expert's clinical experience is the methodology. After the December 2023 amendment to FRE 702, that is no longer accurate. The proponent of the testimony has to show, by a preponderance, that the methodology was reliably applied. A standard-of-care opinion without a named standard cannot meet that burden because the methodology — clinical experience — is not anchored to anything the gatekeeper can evaluate.

The fix is two minutes per opinion. The cost of not making the fix is the entire case.

How to Avoid This in Your Next Case

Three concrete steps:

1. Anchor every standard-of-care opinion to at least one named source. Acceptable sources include: a named professional society guideline (ACOG for OB, ASA for anesthesia, AHA for cardiology, ADA for endocrinology, AANN for neurology), a published clinical practice guideline, a peer-reviewed standard-of-care article, or the institution's own written protocol obtained in discovery. The report should cite the source by name and date — not "professional society guidelines" generally — and quote (briefly, within copyright limits) or paraphrase the relevant language.

2. State the standard, then state the deviation, then state the substantial-factor causation — in that order. The structure forces the report to be complete. The standard is X. The defendant did Y instead. Y deviated from X for these reasons. The deviation was a substantial factor in causing Z. If any of those four pieces is missing, the report is structurally defective.

3. Audit the report against the discovery record before signing. If the institutional protocol is in discovery and the report does not cite it, the defense will. If a society guideline more on-point than the one in the report exists, the defense will surface it. The audit takes an hour. The exclusion takes the case.

A broader point: a standard-of-care opinion is a testable claim. It is testable by the gatekeeper, by the cross-examiner, and by the jury. The reason it is testable is that the standard has a source. An opinion that asserts a standard without naming the source is not a testable claim — it is a credential. After 2023, credentials are not enough.

How a Daubert Workup Tool Can Help

MedLegal AI's Daubert workup tool requires every standard-of-care opinion in a report to be anchored to a named source before the report can be flagged ready for filing. The tool maintains a library of professional society guidelines, clinical practice guidelines, and institutional protocols by specialty, and surfaces the most on-point sources for the case's underlying procedure or condition. It also runs a substantial-factor causation check — flagging any breach opinion that is not paired with an explicit substantial-factor causation statement, the Donnelly failure mode. The point is to prepare smarter for Daubert challenges — to give your expert a report structure that anticipates the gatekeeping order. You can run a free Daubert workup on your expert here.

Bottom Line

Rivera Rodriguez is the cleanest possible cautionary tale for plaintiff med-mal attorneys. A report with the phrase "standard of care" and no named source is a report that can be excluded on the papers, without a Daubert hearing, on a defense motion that takes a paralegal an hour to draft. The fix is two minutes per opinion. The cases that survive Daubert in 2026 will be the ones whose standard-of-care sections name the source, name the deviation, and name the substantial-factor causation.

Run a free Daubert workup on your expert.

MedLegal AI is software, not a law firm. We do not provide legal advice. All AI-generated outputs require independent review by a licensed attorney.

← All posts · About John Mahoney · Free Daubert tool · Start a 14-day free trial