IN THE

SUPREME COURT OF THE STATE OF ARIZONA

MICHELLE SAMPSON, ET AL.

Plaintiff/Appellant,

v.

SURGERY CENTER OF PEORIA, LLC, ET AL.

Defendants/Appellees.

No. CV-20-0024-PR 

Filed July 30, 2021

Appeal from the Superior Court in Maricopa County

No. CV2013-015707

The Honorable Hugh E. Hegyi, Judge (Retired)

The Honorable James Blomo, Judge (Retired)

AFFIRMED

Memorandum Decision of the Court of Appeals

Division One

1 CA CV-18-0113

Filed December 26, 2019

VACATED

COUNSEL:

Arthur E. Lloyd (argued), A. Evan Lloyd, Lloyd Law Group of Arizona, 

P.L.L.C, Payson, Attorneys for Michelle Sampson

DeeDee Armer Holden, Michael J. Ryan (argued), Holden & Armer, P.C., 

Phoenix, Attorneys for Surgery Center of Peoria, LLC

Eileen Dennis GilBride, Jones, Skelton & Hochuli, P.L.C., Phoenix, 

Attorneys for Amicus Curiae Mutual Insurance Company of Arizona
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

Opinion of the Court

2

Peter R. Montecuollo, Shook, Hardy & Bacon, L.L.P., Kansas City, MO; and 

Philip S. Goldberg, Shook, Hardy & Bacon, L.L.P., Washington, DC,

Attorneys for Amicus Curiae American Medical Association and Arizona 

Medical Association

David L. Abney, Ahwatukee Legal Office, P.C. Phoenix, Attorney for 

Amicus Curiae Arizona Association for Justice/Arizona Trial Lawyers 

Association 

____________________

JUSTICE BOLICK authored the Opinion of the Court, in which CHIEF 

JUSTICE BRUTINEL, VICE CHIEF JUSTICE TIMMER, and JUSTICES 

LOPEZ, BEENE, and MONTGOMERY joined.*

____________________

JUSTICE BOLICK, Opinion of the Court:

¶1 We hold today that a jury in a medical malpractice case may 

not be left to “infer” causation without the guidance of expert testimony 

where the cause of death is disputed and not obvious to an ordinary person.

BACKGROUND

¶2 Although the legal issue on which we granted review is 

narrow, precise, and properly decided as a matter of law, the parties have

focused primarily on disputed factual issues that are unnecessary and 

improper for us to resolve.1 As the case was decided in the trial court on a 

∗ Although Justice Andrew W. Gould (Ret.) participated in the oral 

argument in this case, he retired before issuance of this opinion and did not 

take part in its drafting.

1 The Surgery Center did not provide a supplemental brief after we granted 

review. In a case with a dense and extensive record in which the sufficiency 

of expert testimony is at issue, it is highly advisable for a party (particularly 
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

Opinion of the Court

3

motion for summary judgment, “we view the facts and reasonable 

inferences in the light most favorable to the non-prevailing party,” Rasor v. 

Nw. Hosp., LLC, 243 Ariz. 160, 163 ¶ 11 (2017), which is the plaintiff here.

¶3 In March 2012, Sampson took her four-year-old son, Amaré

Burks, to the Surgery Center of Peoria, an outpatient surgery clinic, for a 

scheduled tonsillectomy and adenoidectomy. The procedure is considered 

routine and has an extremely low complication rate. Dr. Guido 

administered the general anesthesia, and Dr. Libling performed the 

procedure. Dr. Libling remained in the operating room with Amaré for 

about thirty minutes after the surgery. At that point, Amaré was sitting up 

and crying and was transferred to a post-operative anesthesia care unit

(PACU).

¶4 Nurse Kuchar attended Amaré in the PACU. Amaré drank 

apple juice and asked for a toy but, according to his mother, appeared 

sleepy and uncomfortable. After sixty-one minutes, Nurse Kuchar released 

Amaré to his mother’s care. He scored eight of eight on a vitals-release test, 

and his condition did not appear concerning.

¶5 Sampson took Amaré home and put him to bed. She had been 

told it was typical for a patient to sleep after surgery. Approximately two 

hours after Amaré’s discharge, Sampson checked on him, and he was not 

breathing. Emergency personnel were unable to revive him.

¶6 Sampson brought a wrongful death action against several 

defendants, including the Surgery Center and Dr. Guido. As required by 

A.R.S. § 12-2603, Sampson identified Dr. Greenberg as her expert witness 

to establish cause of death, proximate cause, and standard of care.

¶7 In his initial affidavit, Dr. Greenberg attested that (1) one hour 

was insufficient to assess a pediatric patient for discharge and that three 

hours was appropriate, especially for a child with a history of sleep apnea; 

(2) the anesthesiologist fell below the standard of care by discharging 

Amaré before that time and Amaré’s death could have been prevented with 

longer observation in the PACU; and (3) Amaré died from being rendered 

unable to breathe from the after-effects of surgery and anesthesia, as his 

the party that lost in the court of appeals) to accept our invitation to further 

brief the specific questions on which we granted review.
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

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4

pharyngeal tissues were swollen and obstructed his upper airway, and the 

residual effects of anesthesia did not allow him to awaken to overcome the 

obstruction. In his deposition, Dr. Greenberg opined that the standard of 

care required between one and three hours of observation before release.

¶8 The Surgery Center and Dr. Guido filed motions for partial 

summary judgment, contending that expert testimony did not establish that 

their actions proximately caused Amaré’s death. At oral argument, 

Sampson’s counsel argued that Dr. Greenberg’s standard-of-care testimony 

was sufficient to establish causation. Pressed by the trial court to identify 

the expert opinion to that effect, counsel acknowledged that ordinarily a 

plaintiff must prove the causal connection through expert testimony

“unless the connection is readily apparent to the trier of fact. And that’s my 

contention, that this is obvious.”

¶9 The trial court granted partial summary judgment for the 

Surgery Center and Dr. Guido, finding that Dr. Greenberg’s testimony 

failed to state a causal connection between the Surgery Center’s actions and 

omissions and Amaré’s death, and that whether Amaré would have 

survived with longer observation involved “matters committed to the 

expertise of medical practitioners, and well beyond the ken of the average 

juror.” The court later entered final judgment against Sampson, and she 

appealed.

¶10 The court of appeals reversed as to the Surgery Center. 

Sampson v. Surgery Ctr. of Peoria, LLC, No. 1 CA-CV 18-0113, 2019 WL 

7187252, at *1 (Ariz. App. Dec. 26, 2019) (mem. decision). Applying Barrett 

v. Harris, 207 Ariz. 374, 378 ¶ 12 (App. 2004), the court articulated the 

baseline principle that “[c]ausation in a medical malpractice action must be 

proved by expert testimony unless the connection between the conduct and 

the injury is readily apparent.” Sampson, 2019 WL 7187252, at *2 ¶ 9. The 

court concluded that “[w]hile expert testimony on causation is often 

necessary, we perceive no such necessity here.” Id. at *4 ¶ 14. 

Acknowledging that Dr. Greenberg’s testimony was “varying widely” 

between one to three hours of observation, the court determined that “a 

reasonable jury could nonetheless find that the standard of care for 

observation was three hours.” Id. at *3 ¶ 13. If it did, the jury “could 

properly infer that the early discharge was the probable cause of Amare’s 

death.” Id.
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

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¶11 We granted review to determine whether the court of appeals 

erred by holding that the jury could properly infer proximate cause under 

the facts presented.2 Whether expert testimony regarding causation is 

required in a medical malpractice case is a recurring issue of statewide 

importance. We have jurisdiction under article 6, section 5(3) of the Arizona 

Constitution.

DISCUSSION

¶12 “Apart from issues of statutory interpretation, which we 

review de novo, we review trial court determinations of expert 

qualifications for an abuse of discretion.” Rasor, 243 Ariz. at 163 ¶ 11

(quoting Baker v. Univ. Physicians Healthcare, 231 Ariz. 379, 387 ¶ 30 (2013)).

¶13 In Arizona medical malpractice cases, causation must be 

established by competent expert testimony, and the narrow exception is 

that a jury may infer such causation if malpractice is “readily apparent.” Id.

at 166 ¶ 32; see also Seisinger v. Siebel, 220 Ariz. 85, 94 ¶ 33 (2009) (noting that, 

absent expert testimony, plaintiff could not meet the burden of production 

under the common law “except when it was ‘a matter of common 

knowledge . . . that the injury would not ordinarily have occurred if due 

care had been exercised’”) (quoting Falcher v. Saint Luke’s Hosp. Med. Ctr., 

19 Ariz. App. 247, 250 (1973)). As the court of appeals here departed from 

that standard to allow a jury to determine causation based on speculation 

built upon inference, we reverse its decision.

¶14 A plaintiff establishes medical malpractice by proving that (1) 

“[t]he health care provider failed to exercise that degree of care, skill and 

learning expected of a reasonable, prudent health care provider in the 

profession or class to which he belongs within the state acting in the same 

or similar circumstances,” and (2) “[s]uch failure was a proximate cause of 

the injury.” A.R.S. § 12-563. The second requirement is at issue here.

¶15 Regarding causation, a plaintiff must show “a natural and 

continuous sequence of events stemming from the defendant’s act or 

omission, unbroken by any efficient intervening cause, that produces an 

injury, in whole or in part, and without which the injury would not have 

2 We improvidently granted review of whether Dr. Greenberg was 

qualified to establish the standard of care for Nurse Kuchar. That issue was 

neither before the trial court nor the court of appeals, and we therefore 

dismiss review of that question.
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

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6

occurred.” Barrett, 207 Ariz. at 378 ¶ 11. Moreover, a plaintiff must show 

that causation is probable, not merely speculative. Robertson v. Sixpence Inns 

of Am., Inc., 163 Ariz. 539, 546 (1990).

¶16 As medicine in general and, more specifically, advanced 

medical techniques involve extensive professional training, in most 

instances the applicable standard of care, and the probable consequences of 

failing to meet that standard, are beyond ordinary lay knowledge. 

Therefore, in a medical malpractice case, “the standard of care normally 

must be established by expert medical testimony.” Seisinger, 220 Ariz. 

at 94 ¶ 33. Thereafter, “[t]o establish the requisite causal connection, the 

plaintiff’s expert is generally required to testify as to probable causes of the 

plaintiff’s injury.” Benkendorf v. Advanced Cardiac Specialists Chartered, 228 

Ariz. 528, 530 ¶ 8 (App. 2012). This Court has recognized that “the 

requirement of expert testimony in a medical malpractice action is a 

substantive component of the common law governing this tort action,”

Seisinger, 220 Ariz. at 95 ¶ 38, and that “failure to produce such a witness 

results in judgment for the defendant,” id. at 94 ¶ 35.

¶17 Here, the plaintiff satisfied the first requirement of § 12-563 

by providing a competent expert witness, Dr. Greenberg, who opined that 

Surgery Center and Dr. Guido fell below the requisite standard of care. 

However, he equivocated over the applicable standard, providing a range 

from one hour of post-operative observation, which the Surgical Center 

satisfied, to up to three hours, which it did not. More significantly, Dr. 

Greenberg did not opine that insufficient observation was the probable 

proximate cause of Amaré’s death. Rather, he opined that greater 

observation “could have” allowed Surgery Center personnel to resuscitate

Amaré.

¶18 Acknowledging the “deficits and contraindications” in Dr. 

Greenberg’s testimony, the court of appeals nonetheless concluded that if 

the jury “were to agree that the standard of care was breached as to time, 

then no expert evidence would be necessary to permit it to infer that a 

discharge in violation of that standard was the probable cause of a death 

that occurred within the time the child should have been observed under 

the standard of care.” Sampson, 2019 WL 7187252, at *3–4 ¶¶ 13–14. In other 

words, a jury may infer causation even where the expert could not, or 

would not, state a precise standard of care nor state that the Surgery 

Center’s deficiency in adhering to the standard of care was the probable 

proximate cause of the death.
SAMPSON, ET AL. V. SURGERY CENTER OF PEORIA, LLC, ET AL.

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¶19 Causation by inference is far more limited than the court of 

appeals recognized. The standard of care must be established by expert 

medical testimony “[u]nless malpractice is grossly apparent,” Rasor, 243 

Ariz. at 163 ¶ 12, and expert causation testimony is necessary unless 

causation is “readily apparent to the jury on the facts,” id. at 166 ¶ 32. In a 

case where the standard of care or the cause of death is disputed on a matter 

requiring medical knowledge to resolve, it is difficult, if not impossible, to 

imagine a situation where lay jurors, untrained in medicine or medical 

procedure, could properly determine liability absent expert guidance. See, 

e.g., W. Bonded Prods. v. Indus. Comm’n of Ariz., 132 Ariz. 526, 527 (App. 1982) 

(“A lay person does not possess the knowledge necessary to make an 

accurate diagnosis or to describe a condition’s etiology. Even a logical 

interpretation of events surrounding the . . . incident . . . , when made by a 

layman, is no more than speculation.”).

¶20 A case comparison is instructive. Morrison v. Acton, which 

involved a dentist who left a piece of metal imbedded in a patient’s jawbone 

that subsequently resulted in severe injury, is a classic example of a case

where a jury could properly infer that the dentist’s negligence was the 

proximate cause. 68 Ariz. 27, 33 (1948). By contrast, Spielman v. Industrial 

Commission of Arizona involved an injury related to multiple surgeries, in 

which “[l]ay logic alone” could not determine the relationship between the 

surgeries and injury. 163 Ariz. 493, 497 (App. 1989). When the expert failed 

to commit to a causation opinion, the court held that the proper result was 

dismissal. Id. at 496–97.

¶21 In this case, expert testimony establishing causation was 

essential. Disagreement existed even over the cause of Amaré’s death. 

Whereas the autopsy report stated that Amaré died from a “disseminated 

Strep Group A” infection, Dr. Greenberg opined he died from a “swollen 

and obstructed upper airway” combined with his inability “to breathe from 

the after-effects of surgery and anesthesia.” Given that even the medical 

experts did not agree on the cause of death, it is unrealistic to conclude, as 

the court of appeals did, that a jury “could properly infer that the early 

discharge was the probable cause of Amare’s death.” Sampson, 2019 WL 

7187252, at *3 ¶ 13.

¶22 As the trial court observed, even if Dr. Greenberg’s testimony 

established that three hours of observation constituted the standard of care, 

“lay jurors are not competent to determine that Amare’ would have 
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exhibited symptoms of distress during those three hours, what those 

symptoms would have been, what a reasonable schedule of observation in 

such a center would have been, whether the Surgery Center would or 

should have noticed Amare’s distress had it observed that schedule, and, if 

it had noted distress, what could have been done in a timely manner to save 

Amare’.” As a result, Sampson did not establish that the failure to observe 

Amaré for a longer period caused his death by starting a natural and 

continuous sequence of events, unbroken by any intervening causes. See 

Barrett, 207 Ariz. at 378 ¶ 11.

¶23 Thus, even if Dr. Greenberg’s testimony regarding causation 

is generously read to require a three-hour observation period, his failure to 

connect the dots between the premature discharge and Amaré’s death 

would leave the jury to infer that Surgery Center’s failure to observe was 

the proximate cause. “Such causation must be shown to be [p]robable and 

not merely [p]ossible, and generally expert medical testimony that a 

subsequent illness or disease ‘could’ or ‘may’ have been the cause of the 

injury is insufficient.” Kreisman v. Thomas, 12 Ariz. App. 215, 218 (1970); 

accord Robertson, 163 Ariz. at 546 (recognizing that causation cannot be left 

to jury speculation). Dr. Greenberg’s assertion that a longer observation

period could have prevented Amaré’s death is therefore insufficient as a 

matter of law to prove causation. See, e.g., Gregg v. Nat’l Med. Health Care 

Servs., Inc., 145 Ariz. 51, 54 (App. 1985) (holding that plaintiff must prove a 

causal relationship between defendant’s actions or omissions and the 

death).

¶24 For the foregoing reasons, the trial court did not err by

granting partial summary judgment.

CONCLUSION

¶25 We affirm the trial court’s ruling and vacate the court of 

appeals’ decision.