[PUBLISH]

IN THE UNITED STATES COURT OF APPEALS

FOR THE ELEVENTH CIRCUIT

________________________

No. 13-10425

________________________

D.C. Docket No. 1:10-cv-03309-WSD

CHRISTINA NICOLE ADAMS, CHRISTOPHER L. ADAMS,

 Plaintiffs-Appellants,

versus

LABORATORY CORPORATION OF AMERICA, 

 Defendant-Appellee.

________________________

Appeal from the United States District Court

for the Northern District of Georgia

________________________

(July 29, 2014)

Before CARNES, Chief Judge, MARTIN and GARZA,

∗ Circuit Judges.

PER CURIAM:

 ∗

Honorable Emilio M. Garza, United States Circuit Judge for the Fifth Circuit, sitting by 

designation.

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2

Christina and Christopher Adams (“the Adamses”) filed a lawsuit against 

Laboratory Corporation of America (“LabCorp”), alleging that its 

cytotechnologists were negligent in failing to identify abnormalities in Ms. 

Adams’s Pap smears and that this negligence caused a delay in her cancer 

diagnosis. LabCorp moved to exclude the testimony of Dr. Dorothy Rosenthal 

concerning the alleged breach of the cytotechnologists’ standard of care and moved 

for summary judgment based on the resulting absence of evidence regarding the 

standard of care. The district court granted both motions, and the Adamses now 

appeal. We reverse the district court’s evidentiary ruling, vacate the grant of 

summary judgment to LabCorp, and remand for further proceedings.

I.

In the 32-month period from January 2006 to September 2008, Ms. Adams

received five Pap smear tests. Her doctor took scrapings from her cervix, put them 

on a slide, and sent that slide to LabCorp for review to determine if there were 

abnormalities in the cells on the slide. Ms. Adams was not diagnosed with cervical 

cancer until August 2009, when she went to her doctor complaining of vaginal 

bleeding. By then, the cancer had metastasized in Ms. Adams’s lymph nodes. The 

Adamses brought suit against LabCorp, alleging that, between 2006 and 2008, the 

LabCorp employees who viewed slides of Ms. Adams’s cells failed to properly 

identify the abnormal cells on those slides that indicated precancerous conditions 

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3

or cancer. They contend that those mistakes by LabCorp’s employees delayed the 

diagnosis and treatment of her condition for several years until after her cancer had

developed and metastasized. 

LabCorp’s method of reviewing samples is as follows. A cytotechnologist 

reviews each Pap smear slide by examining it under a microscope. 

Cytotechnologists are not doctors; they are laboratory professionals trained to 

examine cells using microscopes and to recognize cells that appear abnormal.

1

 If 

any of the cells on the slide has precancerous abnormalities or other indications of 

cancer, the cytotechnologist sends the slide to a pathologist2 for review. If the 

cytotechnologist does not see or recognize any abnormal cells, no pathologist 

reviews the slide.

The Adamses retained Dr. Rosenthal as an expert witness to testify about 

whether LabCorp’s employees breached the standard of care for cytotechnologists

when reviewing Ms. Adams’s slides. Dr. Rosenthal’s qualifications are extensive. 

She has been a Professor of Pathology at the Johns Hopkins School of Medicine 

since 1995 and served as Director of Cytopathology for the Johns Hopkins Medical 

Institutions from 1995 to 2003. She has two board certifications from the 

 1 See 1 Exploring Tech Careers 215 (4th ed. 2009); see also 42 C.F.R. § 493.1483 

(“Standard: Cytotechnologist Qualifications”).

2 A pathologist is a doctor who specializes in “the structural and functional manifestations of 

disease.” Dorland’s Illustrated Medical Dictionary 1416 (31st ed. 2007).

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American Board of Pathology: one in Anatomic and Clinical Pathology, and

another described as an Added Qualification in Cytopathology.3 She served on the 

initial task force that developed the Bethesda System terminology, which is the 

classification system that pathologists and cytotechnologists—including those 

working at LabCorp—use for reporting Pap smear results.4

 She testified in her 

deposition that she also has “over 40 years of experience of training cytotechs.”

Dr. Rosenthal formed her opinion by traveling to Atlanta and reviewing Ms. 

Adams’s slides at LabCorp’s laboratory. She spent about 90 minutes examining 

Ms. Adams’s Pap smear slides, using the same model of microscope that 

LabCorp’s cytotechnologists used. She did not mix in slides from other patients, 

and she already knew that Ms. Adams had been diagnosed with cervical cancer. 

Dr. Rosenthal ultimately concluded that LabCorp’s cytotechnologists’ review of 

Ms. Adams’s slides fell short of the applicable standard of care by failing to 

identify abnormal cells that should have been identified. 

After the discovery period had closed, LabCorp moved to exclude Dr. 

Rosenthal’s testimony concerning the alleged breach of the cytotechnologists’

standard of care. In its motion, LabCorp contended that Dr. Rosenthal’s review of 

 3 Cytopathology is “the study of changes in cells in disease.” Dorland’s Illustrated Medical 

Dictionary 474 (31st ed. 2007).

4 See generally World Health Organization, Comprehensive Cervical Cancer Control: A 

Guide to Essential Practice 39 (2006).

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Ms. Adams’s Pap smear slides was tainted by an unreliable methodology. 

Assuming that Dr. Rosenthal’s testimony was excluded, LabCorp also moved for 

summary judgment based on the absence of evidence regarding the 

cytotechnologists’ standard of care, an essential element of the professional 

negligence claim.

The district court granted LabCorp’s motion to exclude Dr. Rosenthal’s 

testimony based on its conclusion that her methodology did not meet the reliability 

requirement of Federal Rule of Evidence 702.

5 The court characterized her 

methodology as an ipse dixit assessment that could not be meaningfully reviewed 

by other experts. It insisted that she should have used a blinded review to evaluate

Ms. Adams’s slides,

6 citing the litigation guidelines approved by the College of 

American Pathologists (“CAP”) and American Society of Cytopathology (“ASC”)

as evidence that a blinded review was the standard set by the profession. The 

 5 The district court also granted LabCorp’s motions to exclude Dr. Rosenthal’s opinions on 

causation and inadequate “continuous quality improvement” efforts. However, the district 

court’s ruling on Dr. Rosenthal’s standard of care testimony is the only evidentiary ruling before 

us in this appeal. (The Adamses had a second expert witness testify as to causation. Dr. George 

Kemp testified that the cytotechnologists’ failure to identify abnormal cells on Ms. Adams’s 

slide delayed the diagnosis of her cancer by several years and thus prevented her from receiving 

treatment before her precancerous condition became cancerous. So it appears from the record—

though we express no opinion on the matter—that Dr. Rosenthal’s causation testimony was not 

the only causation evidence for the Adamses’ claim based on negligence by LabCorp’s 

cytotechnologists.)

6 There are many forms of blinded review. For purposes of this case, the general defining 

feature of a blinded review that distinguishes it from Dr. Rosenthal’s approach is that, in a 

blinded review, the person reviewing a Pap smear slide does not know (1) the identity of the 

person to whom any particular slide belongs, or (2) the ultimate outcome for that person (i.e., 

whether the person has been diagnosed with cervical cancer).

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district court was troubled by the risk of bias in Dr. Rosenthal’s assessment, based 

on the general risk of review bias in non-blinded reviews,

7 as well as Dr. 

Rosenthal’s deposition statements about her “philosophical bent” toward patients 

later diagnosed with cancer. Finally, the district court observed that Dr. 

Rosenthal’s methodology did not adequately simulate a cytotechnologist’s working 

conditions and circumstances, and that her role as a pathologist is “materially 

different in function and scope” from that of a cytotechnologist. 

After Dr. Rosenthal’s opinion on the standard of care was excluded, the 

district court granted LabCorp’s motion for summary judgment. 

II.

We review for abuse of discretion a district court’s evidentiary ruling under 

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). Gen. Elec. 

Co. v. Joiner, 522 U.S. 136, 141–42 (1997). We defer to the district court unless 

its ruling was “manifestly erroneous.” Tampa Bay Water v. HDR Eng’g, Inc., 731 

F.3d 1171, 1183 (11th Cir. 2013) (quoting Joiner, 522 U.S. at 142). The deference 

we show includes giving the court “considerable leeway in deciding in a particular 

case how to go about determining whether particular expert testimony is reliable.”

Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 152 (1999). Even where a

 7 In her deposition, Dr. Rosenthal defined “review bias” as a form of hindsight bias. She 

explained that, “[a]ny time you go to look at another case somebody else has looked at and 

rendered a diagnosis, you’re biased by what they called it, and you’re also biased if you have any 

additional information.” 

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ruling excluding expert testimony is “outcome determinative” and the basis for a 

grant of summary judgment, our review is not more searching than it would 

otherwise be. Joiner, 522 U.S. at 142–43.

III.

The Adamses contend that the district court abused its discretion in 

excluding Dr. Rosenthal’s testimony.

In Daubert, the Supreme Court explained that trial courts must act as 

“gatekeepers” tasked with screening out “speculative, unreliable expert testimony.” 

Kilpatrick v. Breg, Inc., 613 F.3d 1329, 1335 (11th Cir. 2010) (citing Daubert, 509 

U.S. at 597). In that role, trial courts may consider a non-exhaustive list of factors 

including (1) whether the expert’s theory can be and has been tested; (2) whether 

the theory has been subjected to peer review and publication; (3) the known or 

potential error rate of the technique; and (4) whether the technique is generally 

accepted in the scientific community. Id. Later, in Kumho, the Court explained 

that the gatekeeping function governs all expert testimony based on “scientific 

technical, or other specialized knowledge,” not just scientific testimony. 526 U.S.

at 147–49 (quoting Fed. R. Evid. 702). The Court also stressed that the factors 

identified in Daubert “do not constitute a definitive checklist or test.” Id. at 150

(internal quotation marks omitted). While those factors may help in assessing the 

reliability of scientific or experience-based expert testimony, the district court’s 

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“gatekeeping inquiry must be tied to the facts of a particular case.” Id. (internal 

quotation marks omitted). Furthermore, Kumho emphasized that the goal of 

gatekeeping is to ensure that an expert “employs in the courtroom the same level of 

intellectual rigor that characterizes the practice of an expert in the relevant field.” 

Id. at 152.

Federal Rule of Evidence 702, as amended in response to Daubert and 

Kumho, provides:

A witness who is qualified as an expert by knowledge, 

skill, experience, training, or education may testify in the 

form of an opinion or otherwise if: 

(a) the expert’s scientific, technical, or other specialized 

knowledge will help the trier of fact to understand the 

evidence or to determine a fact in issue;

(b) the testimony is based on sufficient facts or data;

(c) the testimony is the product of reliable principles and 

methods; and

(d) the expert has reliably applied the principles and 

methods to the facts of the case.

We have distilled from Daubert, Kumho, and Rule 702 these three requirements: 

First, “the expert must be qualified to testify competently regarding the matter he 

or she intends to address”; second, the expert’s “methodology . . . must be reliable 

as determined by a Daubert inquiry”; and third, the expert’s “testimony must assist 

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the trier of fact through the application of expertise to understand the evidence or 

determine a fact in issue.” Kilpatrick, 613 F.3d at 1335.

8

 

The district court excluded Dr. Rosenthal’s testimony based on its 

conclusion that her methodology was unreliable.

9

 The court gave four grounds for 

its decision. We address each in turn.

A.

The district court determined that “Dr. Rosenthal’s methodology . . . is an 

ipse dixit assessment that is devoid of any methodology that would allow another 

expert to challenge it in any objective sense.” Adams v. Lab. Corp. of Am., No.

1:10-CV-3309-WSD, 2012 WL 370262, at *15 (N.D. Ga. Feb. 3, 2012). The court

 8 In federal diversity actions, state law (Georgia law in the present case) governs substantive 

issues and federal law governs procedural issues. McDowell v. Brown, 392 F.3d 1283, 1294 

(11th Cir. 2004). The district court did not exclude Dr. Rosenthal’s testimony based on 

substantive Georgia law; it relied on its federal Rule 702 analysis. See infra note 9. So there is 

no substantive state law issue presented on appeal.

9 The district court did not find that Dr. Rosenthal’s testimony failed to meet the first and 

third requirements of Rule 702 (qualification to testify and helpfulness to the jury). The court 

noted that LabCorp “does not dispute [Dr. Rosenthal’s] qualifications under Georgia law or 

Daubert to offer an opinion on the standard of care.” Adams v. Lab. Corp. of Am., No. 1:10-CV3309-WSD, 2012 WL 370262, at *10 (N.D. Ga. Feb. 3, 2012). However, certain language in the 

district court’s opinion suggests that the court may have believed that Dr. Rosenthal was not 

qualified to testify about cytotechnologists’ standard of care, given that her role as a 

cytopathologist is “materially different in function and scope” from that of a cytotechnologist. 

Id. at *16. To the extent that the district court found that Dr. Rosenthal was not qualified to offer 

testimony on the standard of care and excluded her testimony on that ground, it was an abuse of 

discretion to do so. Dr. Rosenthal has stellar qualifications as a cytopathologist, is Boardcertified in cytopathology, has trained cytotechnologists for over forty years, and was on the task 

force that developed the terminology they use. See supra at 3–4. She could hardly have been 

more qualified. Cf. McDowell, 392 F.3d at 1296 (“A physician’s area of expertise necessarily 

encompasses the standard of care applicable to nurses.”).

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criticized her further for “not engag[ing] in a peer-reviewable evaluation because 

her opinion was reached without the implementation of any objective standards or 

controls.” Id. 

The district court’s determination was a “manifestly erroneous” conclusion. 

Tampa Bay Water, 731 F.3d at 1183. Dr. Rosenthal did not make an ipse dixit 

assessment. Her opinion “was based on a widely accepted methodology and 

grounded in the available physical evidence.” United Fire & Cas. Co. v. Whirlpool 

Corp., 704 F.3d 1338, 1342 (11th Cir. 2013). She personally reviewed the 

available physical evidence, which consisted of Ms. Adams’s Pap smear slides that 

had been sent to LabCorp for the Pap tests. Dr. Rosenthal did so using the same 

standard microscope as LabCorp’s cytotechnologists, scanning each slide in the 

same general manner as its cytotechnologists do.

10 She later photographed Ms. 

Adams’s slides and used those photographs in her deposition testimony, marking 

the areas in each picture where she had identified an abnormality. 

Dr. Rosenthal used a well-established classification system to assess the 

cells: the same Bethesda System that LabCorp’s cytotechnologists use. In her 

deposition testimony she went picture-by-picture, pointing to specific places in 

each one where Ms. Adams’s cells showed abnormalities and classifying those 

 10 The only arguably appreciable differences between Dr. Rosenthal’s method and the review 

method for LabCorp’s cytotechnologists is that Dr. Rosenthal (1) already knew that the patient 

whose slides she was reviewing had developed cancer and (2) reviewed slides from just one 

patient. Those differences relate to the lack of blinded review, which we address later. See infra

Sections III.C–D. 

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abnormalities using the same Bethesda classification system that is used by 

LabCorp’s cytotechnologists and nearly every other professional in the field of 

cytopathology. And the Bethesda Atlas, which is maintained by the ASC, provides 

numerous examples of each abnormality that Dr. Rosenthal identified, including 

“classic examples” of abnormal cells as well as “borderline” cells. As Dr. 

Rosenthal explained in her deposition, the images in the Atlas could be used to 

assess whether her opinion was in step with the established standards in the field. 

The fact that Dr. Rosenthal applied an established diagnostic system in which she 

was well versed contributed to the reliability of her methodology. See, e.g., 

Pipitone v. Biomatrix, Inc., 288 F.3d 239, 246–47, 251 (5th Cir. 2002) (reversing 

the district court’s exclusion of a medical expert’s testimony after concluding that 

the expert’s methodology was sufficiently reliable, in part because he formed his 

opinion “based on generally accepted diagnostic principles” that he applied in his 

personal examination of the plaintiff).

In addition to the Bethesda System, Dr. Rosenthal used her extensive 

experience in the fields of cytopathology and cytotechnology to assess whether 

LabCorp’s employees’ failure to identify those cells fell below the standard of 

care. She served on the task force that developed the Bethesda System 

terminology, the same diagnostic system that LabCorp’s cytotechnologists use and 

that she used to review their work. Dr. Rosenthal reviews an average of 150 Pap 

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smear slides every six weeks as part of her duties at Johns Hopkins, and she has

trained cytotechnologists for more than forty years. That experience, as well as her

knowledge of the risk of review bias,11 made her well aware of the conditions and 

limitations of the LabCorp cytotechnologists’ review and of her own review of 

their work.

12 As she explained, the criterion she applied during her review was

“what would I expect a brand new cytotech student the next day after she graduates 

or he graduates to do with this case if they saw it.” Dr. Rosenthal’s application of 

her extensive, relevant experience contributed to the reliability of her 

methodology. See, e.g., Dickenson v. Cardiac & Thoracic Surgery of E. Tenn., 

388 F.3d 976, 982 (6th Cir. 2004) (holding that the district court abused its 

discretion in excluding a doctor’s standard-of-care testimony that was “supported 

by extensive relevant experience”); see also Kilpatrick, 613 F.3d at 1336 (“[T]here 

are instances in which a district court may determine the reliability prong under 

 11 See supra note 7 (defining review bias).

12 During Dr. Rosenthal’s deposition, LabCorp’s counsel asked her about the possibility that 

knowing Ms. Adams’s diagnosis had biased her review of the slides. Dr. Rosenthal began her 

answer by pointing out that she was aware that many false negatives were not the fault of the 

cytotechnologist and referred to a 1989 study in which she participated that showed that fact. 

She then said that in conducting her non-blinded review of Ms. Adams’s slides she had 

considered the position that the cytotechnologists had been in when examining those slides. She 

explained that: 

[W]hen I’m sitting down and I’m going to review, I don’t always expect – even if I have a

lawyer sitting along side [sic] of me – I don’t expect every time to find abnormal cells, 

because I know the frailties of the Pap test, both from a sampling device and from the ability 

to distinguish between benign and reactive. So that bias, I think it depends upon what your 

vent [bent?] is when you’re sitting down reviewing any case.

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Daubert based primarily upon an expert’s experience and general knowledge in the 

field.”). It is difficult to imagine how Dr. Rosenthal’s experience could have been 

more extensive and relevant or contributed more to the reliability of the 

methodology she used.

Dr. Rosenthal formed her opinion by using reliable tools, applying an 

established body of medical knowledge, and drawing on her extensive experience 

in the field.

13 That is not an ipse dixit assessment. The best evidence that it is not 

comes—indirectly—from LabCorp’s own expert witness, Dr. Seena Aisner. She 

used the same general non-blinded approach as Dr. Rosenthal. Dr. Aisner received 

Ms. Adams’s slides from LabCorp and then, without doing a blinded review, 

 13 Our concurring colleague questions our approach because we review Dr. Rosenthal’s 

“methodology” when, in his view, her testimony was based “only on the application of 

professional judgment, not ‘methodology.’” He asserts that “there is no methodology” where the 

expert’s opinion involves only “the application of [medical] knowledge.” In using the 

terminology of methodology we are referring to the manner in which Dr. Rosenthal reviewed the 

slides, applied her medical knowledge and experience, including her familiarity with the 

Bethesda Atlas, and formed her opinion. Whether her approach is called a “methodology” or 

simply “application of professional judgment” does not matter. Whatever the terminology, the 

approach is subject to a reliability inquiry. Our case law is clear that even in cases where the 

reliability determination turns primarily on an expert’s experience, “the district court must still 

determine the reliability of the opinion, not merely the qualifications of the expert who offers it.” 

Kilpatrick, 613 F.3d at 1336. So courts should still consider whether the manner (some might 

say methodology) of applying medical knowledge is itself reliable. See, e.g., In re Paoli R.R. 

Yard PCB Litig., 35 F.3d 717, 762 (3d Cir. 1994) (examining whether “evaluation of the 

patient’s medical records . . . is a reliable method of concluding that a patient is ill even in the 

absence of a physical examination”). If, for instance, Dr. Rosenthal had viewed slides that were 

different from the ones that LabCorp’s cytotechnologists screened (e.g., slides that had been 

taken later than the ones at issue), then her method probably would not be reliable under Rule 

702. See id. As the concurring opinion points out, the application of Daubert is necessarily 

flexible and case specific. Whatever the terminology, we have inquired into the reliability of Dr. 

Rosenthal’s approach and concluded that the district court abused its discretion in finding that 

approach was not reliable. 

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evaluated those slides without mixing in slides from any other patients. She then 

gave her own opinion about each slide, and in her deposition explained why she 

disagreed with Dr. Rosenthal’s opinion. That squarely contradicts the district 

court’s assertion that Dr. Rosenthal’s methodology did not “allow another expert to 

challenge it in any objective sense” and was not “a peer-reviewable evaluation.” 

Adams, 2012 WL 370262, at *15. The methodology not only allowed Dr. Aisner 

to challenge Dr. Rosenthal’s opinion, she did challenge it. 

B.

The district court also concluded that Dr. Rosenthal’s methodology did not 

“satisfy the generally accepted standards in the area of pathology or 

cytotechnology.” Adams, 2012 WL 370262, at *15. Specifically, it faulted her for 

failing to conduct “a blinded review[,] which is the standard set by the profession 

in which Dr. Rosenthal practices.” Id. The court decided that a blinded review 

was the standard set by the profession based on the litigation guidelines created by 

the CAP and ASC. Id. at *12–15. That was an error of law because Daubert and 

Kumho do not allow courts to delegate to potential defendants decisions about 

when and how they may be held civilly liable for their mistakes. And an error of 

law is necessarily an abuse of discretion. See City of Tuscaloosa v. Harcros 

Chemicals, Inc., 158 F.3d 548, 556 (11th Cir. 1998).

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As an initial matter, it is important to put these guidelines in context. Both 

sets of them focus not on how cytotechnologists should go about their duties in 

examining slides, but instead on how courts should go about their duty to 

adjudicate claims against cytotechnologists and similar professionals. In the words 

of the guidelines, they are to be used in assessing Pap smear slides “in conjunction 

with litigation or potential litigation.”14 They are not objective, scientific findings; 

they are not guidelines followed by laboratories to screen for pre-cancerous or 

cancerous cells; they are policy proposals to limit how the courts can find the 

members of the organizations liable for professional negligence when they are 

sued.

15

As far as we are aware, this is the first time that an industry group has 

promulgated a set of guidelines that attempts to define and limit the evidence 

courts should accept when the group’s members are sued.16 The members of the 

CAP and ASC have a substantial interest in making it more difficult for plaintiffs 

 14 The CAP’s guidelines are titled “Guidelines for the Review of Pap Tests in the Context of 

Litigation or Potential Litigation,” while the ASC’s guidelines are titled “Guidelines for Review 

of GYN Cytology Samples in the Context of Litigation or Potential Litigation.”

15 The CAP puts the headline “Policy” above its guidelines. And both sets of guidelines state 

that they are proposals for establishing a method of reviewing Pap test slides “that is fair to both 

the patient and the laboratory.” An assessment of what is “fair” is obviously a value judgment, 

not a scientific finding or standard.

16 At oral argument, we asked counsel for LabCorp if she was aware of any similar 

guidelines from any other private organization or industry group. She replied that she was not.

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to sue based on alleged negligence in their Pap smear screening,17 and their 

guidelines do just that. 

Both sets of guidelines condemn the practice of allowing plaintiffs to use 

expert opinions, like Dr. Rosenthal’s, that are formed based on a review of the 

slides in which the expert already knows the patient has been diagnosed with 

cancer. The ASC says that: “Focused review or review with knowledge of 

subsequent development of carcinoma inevitably biases the objectivity of the 

review against the laboratory and does not reflect standard practice.” And the CAP 

says that: “Focussed [sic] review, or review with knowledge of subsequent 

development of carcinoma, biases the objectivity of the review.” The CAP goes on 

to declare that: “Unless the review is blinded, it cannot establish deviation from 

the standard of practice.” That, of course, is a decision to be made by courts, not 

by self-interested associations.

To address review bias, both sets of guidelines propose that plaintiffs have 

multiple reviewers conduct a “blind” review in which (a) the plaintiff’s slides are 

mixed in with other normal and abnormal slides, (b) those slides are sent to 

multiple reviewers who do not know which slides are the plaintiff’s, and (c) those 

reviewers offer their opinion on which slides are normal and which are abnormal. 

 17 Both organizations reveal their motivation to reduce litigation when they propose, as one 

of their guidelines, that “parties should also strongly consider mediation or non-binding 

arbitration by a panel of individuals trained and having experience in cytopathology before 

proceeding with civil litigation relating to a Pap test.” 

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The guidelines insist that there can be no breach of the duty of care “unless there is

a consistent finding by the reviewers that the laboratory failed to identify clinically 

significant abnormalities.” The guidelines seek to skew the evidentiary rules in 

civil litigation against plaintiffs in at least two ways.

18

The first way is by imposing a requirement on expert testimony for a 

plaintiff that, as far as this Court is aware, no court has ever imposed on standardof-care testimony in professional negligence cases: that an expert witness must 

eliminate any potential “review bias” in her opinion. Bias in an expert witness’s 

testimony is usually a credibility issue for the jury. See United States v. AbonceBarrera, 257 F.3d 959, 965 (9th Cir. 2001); DiCarlo v. Keller Ladders, Inc., 211 

F.3d 465, 468 (8th Cir. 2000). But both sets of guidelines treat the mere risk of 

review bias as intolerable. They do not specify the frequency or degree to which 

review bias actually affects reviewers’ judgments. Nor do they cite any empirical 

evidence supporting their assertion that knowing the outcome “inevitably biases”

the reviewer.19 Yet they insist that a court should exclude expert testimony unless 

 18 The district court did note that it was “not hold[ing] that a blinded review conducted 

pursuant to the College of American Pathologists and American Society of Cytopathology 

litigation slide review guidelines is the only methodology that would allow an expert to offer an 

opinion on the standard of care for a cytotechnologist in reviewing Pap smear slides.” Adams, 

2012 WL 370262, at *17 n.11. The court did not, however, specify what form of blinded review 

short of the kind specified in the CAP and ASC guidelines might suffice. In any event, it is 

apparent that the CAP and ASC guidelines are the lynchpin for the court’s ruling. They are the 

sole support offered for the court’s conclusion that any form of non-blinded review is unreliable. 

19 Both sets of guidelines assert that Pap tests performed on patients have an “irreducible 

false negative rate” of about five percent. But that does not support the claim that non-blinded 

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the expert has eliminated entirely the possibility of any review bias. That would be 

a radical reworking of Rule 702, which requires courts to determine that the

expert’s method is reliable, not that it is free of any possibility of bias.

The second way the guidelines would skew the evidentiary rules against 

plaintiffs is by imposing a one-sided standard for reliability. Both sets of 

guidelines require a blinded review to establish a breach of the standard of care, 

but neither one requires defense experts to base their opinions on a blinded review. 

(Maybe that is why LabCorp’s expert, Dr. Aisner, did not conduct a blinded review 

when she evaluated Ms. Adams’s slides.) For example, the CAP’s guidelines say, 

point blank, that “[o]ne asserting a violation of the standard of care should first 

have the Pap test slides assessed by qualified reviewers without knowledge of 

clinical background and in an environment that simulates normal screening 

practice.” The “one asserting a violation of the standard of care” is, of course, the 

plaintiff. The guidelines impose no similar obligation on expert witnesses for the 

defense. And the ASC’s guidelines condemn non-blinded review because it 

“biases the objectivity of the review against the laboratory,” but express no 

 

reviews are hopelessly subjective and biased. The guidelines themselves reveal that the 

irreducible error rate in initial Pap screening tests is due to “[m]any factors,” and name 

“sampling problems with specimen collection” as one of them. Any sampling problems in the 

collection of the cells could not have affected Dr. Rosenthal’s methodology or her opinion 

because she examined all of the slides examined by the cytotechnologists, not a sample of them. 

The sampling was done before she or the cytotechnologists saw any of the slides. The question 

is what happened after the cells were collected and placed on the slides.

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concern about non-blinded review biasing the assessment of defense experts

against plaintiffs. Clearly, the purpose of the guidelines is to raise the bar only on 

the plaintiffs’ side of the courtroom. 

Despite the skewed nature of the CAP’s and ASC’s guidelines, the district 

court expressed no skepticism about them, referring to their insistence on blinded 

review as “the litigation standard within the practice of pathology.” Adams, 2012 

WL 370262, at *14 (emphasis added). But neither Daubert nor Kumho permits a

scientific or medical community to define a “litigation standard” that applies when 

its members are sued.

Daubert did acknowledge that, where expert testimony is based on a 

scientific technique or theory, courts may consider “the particular degree of 

acceptance” it has in “a relevant scientific community” as an indicator of its 

reliability. 509 U.S. at 594 (internal quotation marks omitted). But the 

“acceptance” to which Daubert refers is the acceptance that the technique or theory 

has in the community’s own field of practice when the science is being applied

outside of the litigation context, not the scientific community’s opinion about the 

standard or type of proof that should be required in litigation. As the Supreme 

Court later acknowledged, “there are important differences between the quest for 

truth in the courtroom and the quest for truth in the laboratory.” Id. at 596–97. 

One of those differences is that the scientific community’s search for truth is 

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20

“subject to perpetual revision” and not driven by the self-interest of parties in 

litigation. Id. at 597.20 

With their guidelines for litigation, the CAP and ASC moved away from 

disinterested scientific inquiry and into litigation policy to serve their members’

own interests. However much the members of those associations may accept and 

even applaud the move, it is not scientific acceptance, which is what Daubert

involves. Nor is litigation policy “the practice of an expert in the relevant field,” as 

Kumho thought of it. See Kumho, 526 U.S. at 152 (stating that the district court’s 

gatekeeper function is meant to ensure that an expert “employs in the courtroom 

the same level of intellectual rigor that characterizes the practice of an expert in the 

relevant field”). The district court’s ruling runs afoul of those two decisions, 

which do not permit delegating to industry groups the gatekeeping duties of the 

courts.

If the CAP and ASC can define what constitutes admissible expert testimony 

in their members’ professional negligence cases, then there is no apparent reason 

why other groups whose members face lawsuits cannot do the same. For example, 

 20 We do not mean to suggest that Daubert’s acceptance factor cannot apply to scientific 

techniques that are primarily applied in law enforcement and the courtroom, such as fingerprint 

analysis and other forensic disciplines. See, e.g., United States v. Abreu, 406 F.3d 1304, 1307 

(11th Cir. 2005); see generally Daubert v. Merrell Dow Pharm., Inc., 43 F.3d 1311, 1317 n.5 

(9th Cir. 1995). Instead, we mean that when analyzing the “general acceptance” factor from 

Daubert, it matters whether an industry group whose expertise lies outside the litigation context 

is advocating a policy position to benefit its members in litigation.

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21

why couldn’t pharmaceutical companies adopt guidelines setting high standards of 

proof for establishing that a plaintiff’s injury was caused by a given drug and 

justify doing so based on their experience with the complex nature of 

pharmacology and their expertise in the field? Why couldn’t an association of 

prison guards and wardens presume to define the meaning of “deliberate 

indifference” or the requirements for admission of evidence in custodial litigation? 

They can’t because courts do not allow interested groups to set evidentiary or other 

litigation standards. 

C.

The district court also determined that, even apart from the guidelines, Dr. 

Rosenthal’s methodology was unreliable because “review bias i[s] inherent” in a

non-blinded review, and she admitted in her deposition that she had a 

“philosophical ‘bent toward a plaintiff who has developed cervical cancer.’” 

Adams, 2012 WL 370262, at *15. In doing that, the district court supplanted the 

jury’s factfinding role.

We have repeatedly stressed Daubert’s teaching that the gatekeeping 

function under Rule 702 “is not intended to supplant the adversary system or the 

role of the jury: ‘vigorous cross-examination, presentation of contrary evidence, 

and careful instruction on the burden of proof are the traditional and appropriate 

means of attacking shaky but admissible evidence.’” United States v. Alabama 

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22

Power Co., 730 F.3d 1278, 1282 (11th Cir. 2013) (emphasis added) (quoting 

Allison v. McGhan Med. Corp., 184 F.3d 1300, 1311–12 (11th Cir. 1999)). That is 

the case here.

At most, LabCorp established that there is an unspecified level of risk that 

Dr. Rosenthal’s assessment might have been biased, and that she had not sought to 

exclude the possibility of bias by conducting a blinded review. See supra note 19

and accompanying text. The risk of bias would mean, at most, that Dr. Rosenthal’s 

testimony is to some extent “shaky,” and shakiness goes to the weight of her 

testimony, not its admissibility. See Ala. Power Co., 730 F.3d at 1282; see also

Rosenfeld v. Oceania Cruises, Inc., 654 F.3d 1190, 1193 (11th Cir. 2011) (“[I]n 

most cases, objections to the inadequacies of a study are more appropriately 

considered an objection going to the weight of the evidence rather than its 

admissibility.” (internal quotation marks omitted)). All of the bias concerns that 

the court raised could have been presented to and considered by the jury. LabCorp 

could cross-examine Dr. Rosenthal to bring out any bias she had and to expose the 

risk of bias inherent in the methodology she used. LabCorp’s attorney did question

Dr. Rosenthal on the subject at great length during her deposition, asking her about 

review bias, the virtue of blinded reviews, and her philosophical bent in favor of 

plaintiffs with cancer. She could have done the same thing before the jury. 

Hindsight bias is a common-sense concept—everyone knows that “hindsight is 

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20/20.” And common-sense concepts are especially appropriate for consideration 

by a jury. See Stollings v. Ryobi Technologies, Inc., 725 F.3d 753, 766 (7th Cir. 

2013) (“The judge should permit the jury to weigh the strength of the expert’s 

conclusions, provided such shortcomings are within the realm of a lay juror’s 

understanding.”). Whether and, if so, the extent to which an expert’s philosophical 

bent biases her review is a credibility determination that has always been within 

the province of the jury. See DiCarlo, 211 F.3d at 468. The same is true of an 

outcome-knowledge bent. The asserted problems with Dr. Rosenthal’s testimony 

could be addressed through the conventional adversarial means and assessed by the 

jury. Absent some other basis for summary judgment, they should be. 

D.

Finally, the district court faulted Dr. Rosenthal’s methodology because her 

“approach did not account for the similar conditions and surrounding 

circumstances under which a cytotechnologist works and originally viewed the 

slides.” Adams, 2012 WL 370262, at *15. The court noted that “[i]t is a 

fundamental principle under Georgia law that the standard of care in medical 

malpractice actions requires that expert opinions take into account ‘similar 

conditions and like surrounding circumstances.’” Id. It then reasoned that Dr. 

Rosenthal’s testimony was unreliable because she had not recreated the conditions 

and circumstances cytotechnologists face because she did not look at a large 

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number of slides without already knowing whether they contained cells that were 

abnormal. Id. at *15–16. Even assuming that Georgia law should apply in Rule 

702 analysis, the district court’s reasoning was manifestly erroneous.

First, the court overlooked Dr. Rosenthal’s experience in training 

cytotechnologists and her deposition testimony explaining that when she reviews 

slides she does consider the conditions under which cytotechnologists conduct 

their review.

21 Second, Georgia courts have not interpreted their malpractice 

standard to require that expert witnesses “stand in the shoes of the defendant” as 

the district court says they must. See, e.g., Hankla v. Jackson, 699 S.E.2d 610, 

612–13 (Ga. Ct. App. 2010) (allowing an expert witness in a medical malpractice 

case to rely on her review of the plaintiff’s medical records in testifying that the 

nurse midwife breached the standard of care). The district court’s reasoning

seemingly would bar all expert medical testimony unless the expert has somehow 

recreated the same conditions that the defendant was under. For example, if a

plaintiff claimed that a defendant doctor prescribed her improper levels of 

medication, the expert could not just review the plaintiff’s medical file to form his 

opinion. After all, the defendant doctor probably saw numerous patients that day

and did so without the benefit of knowing what reaction that a given patient would 

have to a prescription. Under a standing-in-the-shoes requirement, a plaintiff’s file 

 21 See supra note 12 and accompanying text.

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would have to be mixed in with numerous others and then sent to several doctors 

who would recommend prescription levels for all of the patients. The plaintiff 

would have a negligence claim only if those reviewers consistently recommended a 

different level of medication for the plaintiff. Rule 702 does not impose such a 

requirement.

Dr. Rosenthal was qualified to testify about cytotechnologists’ standard of 

care, her methodology was reliable, and her testimony would assist the trier of fact. 

Kilpatrick, 513 F.3d at 1335. Accordingly, the district court abused its discretion 

in excluding her testimony.

IV.

For the foregoing reasons, we REVERSE the district court’s ruling 

excluding Dr. Rosenthal’s opinion on the standard of care for cytotechnologists, 

VACATE the district court’s grant of summary judgment to LabCorp, and 

REMAND for further proceedings consistent with this opinion.

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GARZA, Circuit Judge, specially concurring:

I concur in the judgment and in the majority’s conclusion that the district 

court abused its discretion in excluding Dr. Rosenthal’s testimony. I also agree 

with the majority’s reasoning with the exception of its discussion of Dr. 

Rosenthal’s “methodology,” primarily in Part III.A. In my view, Dr. Rosenthal’s 

testimony on the standard of care and its alleged breach in this case is admissible 

because her qualifications and experience are sufficient. Under Federal Rule of 

Evidence 702 and Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 

(1993), this case does not implicate any “methodology.” Rather, the reliability of 

Dr. Rosenthal’s testimony on the standard of care and its alleged breach depends 

only upon her knowledge of the abnormalities that a Laboratory Corporation of 

America (“LabCorp”) cytotechnologist should be capable of detecting in Pap 

smear slides.

A.

Implicit in the majority’s analysis is that the admissibility of Dr. Rosenthal’s 

opinion hinges on the reliability of her “methodology.” Ante at 9. Although that 

methodology is never precisely defined, the majority mentions Dr. Rosenthal’s 

“personally review[ing] the available physical evidence, which consisted of Ms. 

Adams’s Pap smear slides,” “using the same standard microscope as LabCorp’s 

cytotechnologists,” “scanning each slide in the same general manner as its 

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cytotechnologists do,” and “photograph[ing] Ms. Adams’s slides and us[ing] those 

photographs in her deposition testimony.” Id. at 10. In the majority’s view, 

moreover, the fact that Dr. Rosenthal “applied an established diagnostic system in 

which she was well versed,” id. at 11, and “appli[ed] . . . her extensive, relevant 

experience contributed to the reliability of her methodology,” id. at 12.

In my view, the majority’s attention to “methodology” misses the mark. The 

majority fails to focus on the record evidence that illuminates the exact dispute 

before us—namely, the specifics of a cytotechnologist’s task and the manner in 

which Dr. Rosenthal formed her opinion about Ms. Adams’s slides. 

Cytotechnologists are responsible for screening Pap smear slides for signs of 

disease and malignancy. A single slide can contain thousands of cells, and 

cytotechnologists must flag for further review by a pathologist any cells that might 

be cancerous or precancerous. This determination is guided by the Bethesda 

System, an atlas of images containing various “classic examples” of 

cytomorphologic features.1

 In Dr. Rosenthal’s words, properly trained 

cytotechnologists will “know what benign looks like” when they “decide whether 

or not they’re going to send [the slide] on to the pathologist.” Without constant 

practice in this “qualitative, subjective skill,” even Dr. Rosenthal requires “a few 

days . . . to ‘get [her] eye back.’” A cytotechnologist’s task, then, involves not a 

 1 As the Adamses note, the Bethesda System’s atlas containing its images and classifications can 

be found online at http://nih.techriver.net/index.php.

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“methodology,” but judgment—refined and disciplined through training, practice, 

and knowledge of cytomorphologic features so that one is capable of detecting 

abnormalities. 

This professional judgment underlies Dr. Rosenthal’s testimony about a 

cytotechnologist’s standard of care and the LabCorp cytotechnologists’ alleged 

breach of that standard. In her deposition, Dr. Rosenthal explained the “standard 

of care” as “what a recent graduate of a cytotechnology training program would be 

able to detect under normal screening conditions on a particular slide as an 

abnormality”—a domain of knowledge with which she is intimately familiar, 

having trained cytotechnologists for forty years. As for the alleged breach of the 

standard of care, Dr. Rosenthal’s expert report concluded that on numerous 

occasions, LabCorp cytotechnologists “misinterpreted” Ms. Adams’s Pap smear 

slides and that these errors accordingly “fell below the standard of care for a 

cytotechnologist.”2

 These opinions on the alleged breach followed from her visual 

observation of Ms. Adams’s slides and were “based on over 40 years of 

professional experience at two major medical centers in which [her] career was 

 2 For instance, Dr. Rosenthal’s report claimed: “The March 20, 2008 Pap test was misinterpreted 

by cytotechnologists Robert Allison and Greg McDaniel, as showing ‘NILM [negative for 

intraepithelial lesion and malignancy] with squamous component cells present’. This error in 

interpretation fell below the standard of care for a cytotechnologist.” Dr. Rosenthal’s affidavit 

elaborates on her opinion as to the correct assessment of the March 20, 2008 test: “The test 

actually revealed HSIL [high-grade squamous intraepithelial lesion] with endocervical 

component cells present,” where HSIL is a “high grade cervical cancer precursor condition.” 

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devoted to cytologic interpretation.”3 In addition to her experience, Dr. Rosenthal 

relied on the Bethesda System classifications, which, again, are the same as those 

used by the cytotechnologists in this case. 

Both the cytotechnologist’s task and Dr. Rosenthal’s review involve only the 

application of professional judgment, not “methodology.”4

 The majority, however, 

erroneously conflates scientific knowledge with scientific “methodology.” To be 

sure, both LabCorp cytotechnologists and Dr. Rosenthal applied knowledge 

derived through a scientific methodology—i.e., knowledge of the various cell 

classifications catalogued in the Bethesda System, whose validity is not in 

 3 As the majority explains, Dr. Rosenthal has been a pathology professor since 1995, served on 

the task force that developed the Bethesda System used by cytotechnologists for reporting Pap 

smear results, and has over forty years of experience in training cytotechnologists. Ante at 3–4. 

4 The majority asserts that “[w]hether [Dr. Rosenthal’s] approach is called a ‘methodology’ or 

simply ‘application of professional judgment’ does not matter.” Ante at 13 n.13. But words do 

matter to trial courts tasked with ensuring the reliability of expert testimony under Rule 702 and 

Daubert. Here, Dr. Rosenthal’s application of her knowledge of the standard of care and 

identification of an alleged breach do not implicate a methodology warranting independent 

scrutiny. By contrast, in Daubert and Kumho Tire, the Supreme Court assessed the 

methodologies of experts who sought to testify, respectively, that a particular drug caused birth 

defects and that a tire’s manufacturing or design defect caused its failure. See Daubert, 509 U.S. 

at 593 (“Scientific methodology today is based on generating hypotheses and testing them to see 

if they can be falsified; indeed, this methodology is what distinguishes science from other fields 

of human inquiry.”); Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 153–54 (1999) (“[T]he 

specific issue before the court was not the reasonableness in general of a tire expert’s use of a 

visual and tactile inspection to determine whether overdeflection had caused the tire’s tread to 

separate from its steel-belted carcass. Rather, it was the reasonableness of using such an 

approach, along with [the expert’s] particular method of analyzing the data thereby obtained, to 

draw a conclusion regarding the particular matter to which the expert testimony was directly 

relevant.”).

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dispute.5 But in the application of this knowledge, there is no methodology; the 

observer merely views a slide and forms her judgment based on her knowledge. 

B.

Because the admissibility of Dr. Rosenthal’s testimony hinges on the 

reliability of her knowledge of a cytotechnologist’s standard of care rather than the 

reliability of any “methodology,” her competence renders her testimony admissible 

under McDowell v. Brown, 392 F.3d 1283 (11th Cir. 2004).

In McDowell, this Circuit held that the competency of a standard-of-care 

expert satisfies the demands of Rule 702 and Daubert. In that case, McDowell 

brought a medical negligence suit under Georgia law against Wexford Health 

Sources, which provided medical services in the jail in which he was detained. Id. 

at 1286–87. McDowell alleged that despite his symptoms of severe pain, 

Wexford’s nurse negligently failed to arrange for his timely transport to a nearby 

hospital for treatment, and that this delay proximately caused his partial paraplegia. 

Id. To support his claim, McDowell sought to have three doctors testify that 

Wexford’s nurse breached the standard of care applicable to nurses. The district 

court, however, excluded his experts’ testimony on the basis that they were 

 5 The majority, notably, does not claim that the Bethesda System itself is a “methodology,” but 

only that Dr. Rosenthal’s use of that “well-established classification system” “contributed to the 

reliability of her methodology.” Ante at 10–11.

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“unqualified to render an opinion as to the standard of care applicable to nurses.” 

Id. at 1296.

On appeal, this Court reversed the district court’s ruling, basing its 

determination on the experts’ competency, without mention of any “methodology.” 

The panel began by explaining that the admissibility of standard-of-care expert 

testimony hinges on both state substantive law and federal procedural law: “[I]f a 

witness is deemed competent to testify to the substantive issue in the case [under 

state law], such as the standard of care, his or her testimony should then be 

screened by Rule 702 to determine if it is otherwise admissible expert testimony.” 

Id. at 1295 (quoting Legg v. Chopra, 286 F.3d 286, 292 (6th Cir. 2002) (emphasis 

added)). Next, the panel explained that under Georgia law, a standard-of-care 

expert in a medical malpractice case must possess “knowledge of the standard of 

care applicable to the defendant-professional as to at least one of the matters on 

which the plaintiff’s malpractice claim is based.” Id. at 1296 (citation omitted). 

The panel reasoned that because “[a] physician’s area of expertise necessarily 

encompasses the standard of care applicable to nurses,” id., “the experts [were] 

competent to render opinions as to the applicable standard of care for Wexford’s 

nurses,” id. at 1297. 

The panel ultimately concluded that “the district court erred in excluding the 

experts’ testimony as to the applicable standard of care.” Id. at 1301. To be sure, 

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the panel did not expressly assess the standard-of-care testimony under either Rule 

702 or Daubert.

6

 However, the panel’s earlier conclusion that these federal 

evidentiary rules govern the standard-of-care expert testimony in addition to state 

substantive law, id. at 1295, can only mean that the doctors’ competency under 

Georgia law was also sufficient to satisfy both Rule 702 and Daubert.

7

McDowell governs this case. Here, like the doctors in McDowell, Dr. 

Rosenthal was amply competent to testify about the alleged breach of the standard 

of care in light of her “knowledge of the standard of care applicable to the 

defendant-professional.” Id. at 1296. Indeed, the parties do not dispute her 

competency, ante at 9 n.9, and the majority acknowledges Dr. Rosenthal’s 

“extensive” qualifications, id. at 3. Moreover, neither McDowell nor this case 

implicates a “methodology”; rather, both cases involve the expert’s application of 

professional knowledge to certain facts. Here, those facts were contained on Ms. 

Adams’s Pap smear slides; in McDowell, they took the form of McDowell’s acute 

symptoms. McDowell, 392 F.3d at 1286–87. So long as Dr. Rosenthal has applied 

 6 By contrast, the McDowell panel explicitly applied Rule 702 and Daubert in concluding that 

the district court did not abuse its discretion in excluding expert testimony about causation, since 

the experts offered little support for their belief that McDowell’s treatment delay caused his 

injury. McDowell, 392 F.3d at 1297–1301.

7 For this reason, the majority incorrectly distinguishes McDowell on the grounds that “there is 

no substantive state law issue presented on appeal.” Ante at 9 n.8. McDowell is the leading 

authority in this Circuit on the admissibility of medical malpractice standard-of-care expert 

testimony under federal procedural law, and stands for the proposition that such testimony is 

admissible under Rule 702 and Daubert so long as the expert is competent under state law. 

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medical or scientific knowledge in evaluating the actions or omissions of a 

cytotechnologist, her opinion is reliable.8

Accordingly, under McDowell, Dr. Rosenthal’s opinion about the alleged 

breach of the cytotechnologist’s standard of care is reliable and admissible.

C.

McDowell’s recognition that standard-of-care expert testimony generally 

originates in professional judgment accords with this Circuit’s case law on Daubert

and with the decisions of several other circuits.

Experts testifying on the breach of a standard of care opine on the content of 

that standard and whether a party’s behavior deviated from it. When such opinions 

are empirical, professional judgments, they are based on “reliable principles and 

methods” so long as they are derived from the expert’s competency and 

qualifications. Fed. R. Evid. 702(c); see also Palandjian v. Foster, 842 N.E.2d 

916, 923 & n.12 (Mass. 2006). Such testimony generally does not require devising 

new analyses to explain factual phenomena—an inquiry for which Rule 702 and 

Daubert’s concern with “methodology” is quintessentially important.9

 Nor must 

such experts precisely replicate a litigant’s circumstances before they may opine on 

an alleged breach of the standard of care under those circumstances; hence, the 

 8 Of course, once admitted, Dr. Rosenthal’s testimony would be subjected to the rigors of crossexamination. See ante 21–22.

9 See supra note 4.

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majority correctly rejects LabCorp’s contention that Dr. Rosenthal must “stand in 

the shoes” of actual cytotechnologists. Ante at 24–25. To be sure, the professional 

knowledge underlying testimony about the breach of a standard of care may have 

scientific bases—as in Dr. Rosenthal’s case here, and in the case of the doctors in 

McDowell.

10 But as explained above, the application of scientific knowledge does 

not necessarily implicate a “methodology.”

McDowell’s attention to competency rather than methodology accords with 

this Circuit’s flexible, context-sensitive application of Daubert. We recognize that 

“there are instances in which a district court may determine the reliability prong 

under Daubert based primarily upon an expert’s experience and general 

knowledge in the field.” Kilpatrick v. Breg, Inc., 613 F.3d 1329, 1336 (11th Cir. 

2010) (citing United States v. Brown, 415 F.3d 1257 (11th Cir. 2005)) (emphasis 

added). We have further noted that “Daubert’s list of specific factors neither 

necessarily nor exclusively applies to all experts or in every case.” Brown, 415 

F.3d at 1267 (quoting Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 141 

(1999)). These principles find further support in the Advisory Committee Note’s 

explanation that “the text of Rule 702 expressly contemplates that an expert may 

be qualified on the basis of experience.” Fed. R. Evid. 702 advisory committee’s 

 10 In addition to scientific disciplines, an expert’s knowledge subject to Rule 702 and Daubert

can originate from other “technical” or “specialized” fields of inquiry. See Kumho Tire, 526 

U.S. at 149. Here, however, Dr. Rosenthal’s knowledge certainly has a scientific basis.

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35

note (2000 Amendments) (emphasis added). The Note continues: “If the witness is 

relying solely or primarily on experience, then the witness must explain how that 

experience leads to the conclusion reached, why that experience is a sufficient 

basis for the opinion, and how that experience is reliably applied to the facts.” Id.; 

see also Kumho Tire, 526 U.S. at 156 (“[N]o one denies that an expert might draw 

a conclusion from a set of observations based on extensive and specialized 

experience.”). As in McDowell, and as permitted by Kilpatrick, Dr. Rosenthal’s 

“experience and general knowledge” are sufficient to satisfy Rule 702 and 

Daubert. Kilpatrick, 613 F.3d at 1336.

Similarly, several other courts of appeals applying Rule 702 and Daubert to 

standard-of-care expert testimony have determined that the testimony in question is 

admissible so long as the expert is competent or qualified. See, e.g., Dickenson v. 

Cardiac & Thoracic Surgery of E. Tenn., P.C., 388 F.3d 976, 980–82 (6th Cir. 

2004) (cardiac thoracic surgeon could testify about standard of care of 

pulmonologist on basis of “extensive relevant experience,” id. at 982, and was not 

required to demonstrate familiarity with pulmonology literature or standards); 

Sosna v. Binnington, 321 F.3d 742, 745–46 (8th Cir. 2003) (concluding that 

internist was “competent,” id. at 746, to testify about standard of care of surgeon, 

based on expertise and experience treating patients who underwent surgeries); 

Schneider ex rel. Estate of Schneider v. Fried, 320 F.3d 396, 405–409 (3d Cir. 

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2003) (concluding that two experts were competent to testify about standard of 

care based, respectively, on “experience,” id. at 406, and “qualifications,” id. at 

409). 

McDowell sets forth a sound general rule for screening expert testimony on 

the breach of a standard of care, and I would apply it here.

D.

By failing to delineate the boundaries of Dr. Rosenthal’s “methodology,” 

today’s opinion neglects to explain when courts must depart from McDowell and 

undertake this additional assessment of “methodology.”

The majority struggles to define Dr. Rosenthal’s “methodology.” In an 

apparent attempt, the majority observes that Dr. Rosenthal “personally reviewed 

the available physical evidence,” “us[ed] the same standard microscope as 

LabCorp’s cytotechnologists,” “scan[ned] each slide in the same general manner as 

its cytotechnologists do,” and later “photographed Ms. Adams’s slides.” Ante at 

10. However, this ad hoc list of activities offers no principled explanation of 

where Dr. Rosenthal’s “methodology” begins and ends. Adding to the confusion, 

the majority claims that Dr. Rosenthal need not “stand in the shoes of the 

defendant” by “recreat[ing] the conditions and circumstances cytotechnologists 

face”—that is, reviewing “a large number of slides without already knowing 

whether they contained cells that were abnormal.” Id. at 23–24. While I agree that 

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37

replicating the exact circumstances of a cytotechnologist is wholly unnecessary, 

supra Part C, I can discern no analytical principles in the majority opinion for 

determining when an expert uses a methodology.

Because of the majority’s inability to define Dr. Rosenthal’s purported 

methodology, future courts have no guidance as to when scrutiny of 

methodology—an exception to McDowell—is required in the first place. In certain 

cases, I would agree that courts must validate the reliability of an expert’s 

methodology.

11 For instance, to prove a breach of the standard of care, an expert 

might be called upon to establish the speed of a car at the moment of impact, or the 

temperature of a coffee when spilled.12 But at least here, where the expert simply 

applies her professional judgment to the same facts that confronted the litigant,

McDowell applies.13

 11 Experts attempting to demonstrate causation often deploy methodologies to test whether a 

certain causal hypothesis has factual support. See, e.g., Kilpatrick, 613 F.3d at 1336–43 

(reviewing differential diagnosis methodology employed by expert testifying on causation and 

concluding that district court did not abuse discretion in excluding testimony for lack of reliable 

methodology); see also Guinn v. AstraZeneca Pharms. LP, 602 F.3d 1245, 1252–56 (11th Cir. 

2010) (same); see also supra note 4 (discussing “methodology” at issue in Daubert and Kumho 

Tire).

12 See also Rosenfeld v. Oceania Cruises, Inc., 654 F.3d 1190, 1193 (11th Cir. 2011) (explaining 

that “[a] qualified expert who uses reliable testing methodology may testify as to the safety of a 

defendant’s choice of flooring, determined by the surface’s coefficient of friction”); Lees v. 

Carthage College, 714 F.3d 516, 524 (7th Cir. 2013) (noting that even if parties did not dispute 

expert’s qualifications, assessment of reliability of expert’s testimony about college’s alleged 

breach of standard of care required further analysis of soundness of his “methodology”). 13 Moreover, as in McDowell, the conduct of the defendant is undisputed and requires no factual 

analysis by the expert: Here, the LabCorp cytotechnologists did not flag abnormalities for further 

review by a pathologist. For the purposes of this appeal, the only issue is whether this conduct 

breached the applicable standard of care.

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38

* * *

As the majority correctly explains, Rule 702 and Daubert govern all expert 

testimony based on “scientific, technical, or other specialized knowledge.” Ante at 

7 (quoting Kumho Tire, 526 U.S. at 149). I thus agree that the gatekeeping inquiry 

under Rule 702 and Daubert applies to Dr. Rosenthal’s testimony, which is 

certainly based on “scientific” knowledge.

At bottom, the majority and I disagree over the meaning of “methodology” 

and its role in the gatekeeping inquiry in this particular case.14 In my view, neither 

the LabCorp cytotechnologists nor Dr. Rosenthal applied a methodology in 

assessing Ms. Adams’s Pap smear slides; rather, they simply drew upon their 

knowledge in viewing those slides. Therefore, under McDowell, the reliability of 

Dr. Rosenthal’s testimony on a cytotechnologist’s standard of care and its alleged 

breach depends only on the reliability of her knowledge—i.e., her competency. 

Accordingly, because no party disputes that Dr. Rosenthal is competent to testify 

 14 The Supreme Court has not had occasion to clarify the meaning of “methodology,” though the 

term has given rise to some disagreement among the Justices. In General Electric Co. v. Joiner, 

522 U.S. 136 (1997), the Court noted that “conclusions and methodology are not entirely distinct 

from one another,” and that although “[t]rained experts commonly extrapolate from existing 

data,” “nothing . . . requires a district court to admit opinion evidence that is connected to 

existing data only by the ipse dixit of the expert.” Id. at 146. Justice Stevens, in dissent, 

explained that the Court incorrectly blurred the line between methodology and conclusions, 

which he analogized to the conceptual difference between “means and ends.” Id. at 155 

(Stevens, J., dissenting). Justice Stevens claimed that the expert had reviewed the studies under 

a “‘weight of the evidence’ methodology,” which was reliable enough to deem his testimony 

admissible and allow a jury to assess the soundness of his conclusions. Id. at 152–54 (Stevens, 

J., dissenting).

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on the standard of care and its alleged breach, I would hold that the district court 

abused its discretion in excluding her testimony.

Case: 13-10425 Date Filed: 07/29/2014 Page: 39 of 39