In the

United States Court of Appeals

For the Seventh Circuit ____________________

No. 17-2068

CHARLOTTE ROBINSON and

BOBBY DON BOWERSOCK as co-personal 

representatives of the Estate of 

Georgia J. Bowersock, deceased, and 

MARK BOWERSOCK, individually,

Plaintiffs-Appellants,

v.

DAVOL INC. and C.R. BARD, INC.,

Defendants-Appellees.

____________________

Appeal from the United States District Court for the 

Southern District of Indiana, Indianapolis Division.

No. 1:08-cv-01313-LJM-TAB — Larry J. McKinney, Judge.

____________________

ARGUED FEBRUARY 13, 2018 — DECIDED JANUARY 22, 2019

____________________

Before SYKES and BARRETT, Circuit Judges, and GRIESBACH, 

Chief District Judge.∗

 ∗ Of the Eastern District of Wisconsin, sitting by designation.
2 No. 17-2068

SYKES, Circuit Judge. C.R. Bard, Inc., manufactures a surgical mesh patch used to repair hernias by implantation. The 

patch consists of two pieces of mesh that surround a flexible 

plastic ring. During a hernia repair, the patch is folded to fit 

through a small incision, then the plastic ring springs back 

into its original shape and flattens the mesh against the 

abdominal wall. 

Bard recalled several versions of the patch in late 2005 

and early 2006 following reports that the plastic ring was 

defective. Sometimes the ring broke, exposing a sharp edge 

that could perforate the patient’s intestines. Other times the 

ring caused the patch to bend and warp, exposing the patch’s 

adhesive to a patient’s viscera. 

Prior to the recall, Georgia Bowersock underwent surgery to repair a hernia, and her surgeon implanted a Bard 

patch. Roughly one year later, on October 31, 2006, she died 

of complications arising from an abdominal-wall abscess. 

Her estate and family members sued Bard and Davol Inc., 

the patent holder for the patch, alleging that a defect in the 

patch caused her death. To establish medical causation, the 

plaintiffs retained three experts to opine on the defect and 

the likely cause of Mrs. Bowersock’s death. 

But the experts had trouble establishing causation. Unlike defective patches in other injured patients, 

Mrs. Bowersock’s patch did not adhere to her bowel or 

perforate her organs with a broken, sharp edge. One expert 

tried to present a new theory of causation: the patch had 

“buckled,” forming a stiff edge that rubbed against and 

imperceptibly perforated her internal organs.
No. 17-2068 3

The defendants moved to exclude the expert testimony. 

The judge granted the motion, finding that the “buckling”

theory was not sufficiently reliable. Lacking expert testimony to establish causation, the plaintiffs could not prove their 

case, and the judge entered summary judgment for Bard and 

Davol. 

We affirm. The novel theory of causation was not peer 

reviewed, professionally presented, consistent with 

Mrs. Bowersock’s medical records or autopsy, or substantiated by other cases. The judge therefore did not abuse his 

discretion in excluding the expert testimony. Summary 

judgment for the defendants necessarily followed. 

I. Background

The Composix® Kugel Patch is a prescription medical 

device designed to repair hernias. Bard manufactures the 

patch and Davol owns the patent. (We refer to them collectively as “Bard.”) The patch consists of two layers of mesh 

that surround one or two flexible plastic rings called 

memory rings. The top layer is made of polypropylene; it 

adheres to the abdominal wall under the hernia and facilitates healing. The bottom layer is made of smooth expanded 

polytetrafluorethylene; it faces the bowel to prevent the 

patch from attaching to the viscera. To implant the patch, a 

physician folds the device and then inserts it into the patient 

via a small incision. After insertion the memory ring springs

back and flattens the patch against the abdominal wall. The 

patch remains in the body after the hernia heals.

The patch hit the market in 2001. Users soon began reporting problems with the plastic ring. Sometimes it would 

altogether fail. Other times the ring would experience “buck-
4 No. 17-2068

ling”—that is, the mesh components of the patch would 

contract, causing the ring to resist and bend, kink, break, or 

buckle. Although the patch came with instructions for use 

that contained user warnings, none of the warnings mentioned any of these problems with the plastic ring. On 

December 22, 2005, Bard recalled all extra-large models. 

Several months later Bard expanded the recall to include 

other models.

On May 25, 2005, Mrs. Bowersock sought medical treatment for an abdominal-wall hernia. On July 22 Dr. Mark O. 

Lynch performed surgery and implanted a Bard patch, using 

a model that was included in the second recall. Dr. Lynch

testified that he would not have implanted the patch if he 

had known about the defective memory rings.

On October 4, 2006, Mrs. Bowersock went to the emergency room with an abdominal-wall abscess. The hospital 

cultured the abscess, and the lab results returned positive for 

staphylococcus aureus. Doctors administered antibiotics, 

drained the abscess, and released her from the hospital. She 

returned several days later with a large wound infection. 

While hospitalized she suffered a cardiac arrest. She was 

resuscitated and placed on a ventilator. The hospital took a 

second culture that indicated the presence of staphylococcus 

epidermidis and enterococcus faecalis, or fecal bacteria. A 

third culture returned positive for pseudomonas aeruginosa 

and yeast. Her condition deteriorated until her death on 

October 31, 2006.

Dr. Roland Kohr, the county coroner, performed an autopsy that same day and determined that pneumonia and 

complications of that disease ultimately caused

Mrs. Bowersock’s death. In his report Dr. Kohr noted 
No. 17-2068 5

“abdominal adhesions” and an “abdominal wall fistula.” He 

also noted that the “small bowel and colon [were] intact 

without perforation, diverticula or palpable tumors.”

Dr. Kohr later exhumed Mrs. Bowersock’s body and retrieved the implanted patch for further study.

Bobby and Mark Bowersock (Mrs. Bowersock’s sons) and

Charlotte Robinson (her sister) sued Bard in federal court

raising claims of negligence, failure to warn, breach of 

implied warranty, fraud, and intentional infliction of emotional distress. They also asserted a statutory claim for 

violation of the Indiana Deceptive Consumer Sales Act, IND.

CODE § 24-5-5. Bobby and Charlotte are co-representatives of 

Mrs. Bowersock’s estate; Mark also asserted an individual 

claim under the Indiana Wrongful Death Act, id. § 34-23-1-1.

All of the claims rested on the same essential allegations: the 

patch implanted in Mrs. Bowersock was defective and 

ultimately caused her death. The district court consolidated 

the claims under the Indiana Products Liability Act, id.

§§ 34-20-1-1 et seq., which “govern[s] all product liability 

actions, whether the theory of liability is negligence or strict 

liability in tort,” Dague v. Piper Aircraft Corp., 418 N.E.2d 207, 

212 (Ind. 1981). 

The plaintiffs retained Dr. Stephen Ferzoco to opine on 

the cause of death. Dr. Ferzoco has experience treating

patients who had problems with the patches. He also has

testified in cases where the memory ring broke or the polypropylene side of the patch adhered to the intestines. After 

examining the patch that was retrieved from 

Mrs. Bowersock, however, Dr. Ferzoco conceded that neither 

of those problems had occurred here. He instead developed 

a new theory to account for her injury: the ring had buckled 
6 No. 17-2068

but stayed intact, and the raised portion of the mesh 

“rubb[ed] up against the bowel causing a fistula or break 

and then seal[ed] up prior to explantation or discovery of the 

mesh in the bowel.” The parties and the district judge referred to this as the “nidus” theory (meaning the location or 

focus of an infection), so we do the same; here it describes

the location where Dr. Ferzoco theorized that the buckled 

ring rubbed against the bowel. Dr. Ferzoco also testified that 

he could rule out several other possible causes of death, 

including cross-contamination of fecal matter, fecal matter 

entering through the skin, obesity, diabetes, and chronic 

obstructive pulmonary disease.

Dr. Ferzoco’s theory was novel: he had never before presented it in a formal or professional setting and could not 

identify published medical literature discussing it. Though 

he claimed to have seen this particular malfunction occur in 

other patients, he declined to identify the patients or produce their medical records. Crucially, he admitted that there 

was no evidence in the medical records or autopsy report of 

bowel erosion or perforation. 

The plaintiffs also retained Dr. William Hyman, a professor of biomedical engineering. He opined that the memory 

ring’s design was inherently dangerous, that Bard failed to 

adequately test the patch, and that feasible alternative 

designs were available. He also speculated that based on the 

defective design and Dr. Ferzoco’s medical testimony, the 

ring buckling likely caused the bowel injury. He identified

two important limitations in his testimony, however. First, 

he admitted that he never examined or viewed images of 

Mrs. Bowersock’s patch. Second, he is “not a microbiologist 
No. 17-2068 7

and [was] not offering an independent opinion on the microbiology of her infection.”

Finally, the plaintiffs retained Dr. Kohr, the coroner. He 

reiterated in his deposition that the autopsy did not reveal

any visible breaches of the small bowel or colon. He clarified, however, that “there could have been superficial 

breaches scarred over with additional inflammation” and 

that “extensive adhesions in the suprapubic area [and] lower 

abdomen” suggested the “possibility” of a breach. He also 

testified that at the time of the autopsy, he wasn’t aware of 

the problems with the patch or Bard’s recalls. Dr. Kohr 

concluded that there was a “reasonable medical probability”

that the patch caused Mrs. Bowersock’s death.

Bard moved to exclude the causation opinions offered by 

each of these experts, arguing that (1) Dr. Ferzoco’s nidus 

theory was not reliable; (2) Dr. Hyman’s opinion was unsupported by the medical records; and (3) the plaintiffs 

failed to timely disclose Dr. Kohr as an expert under Rule 26

of the Federal Rules of Civil Procedure. Bard also sought 

summary judgment, arguing the plaintiffs could not prove 

that the patch or its warnings were defective or caused 

Mrs. Bowersock’s death.

The judge granted the motion to exclude the experts. He 

ruled that Dr. Ferzoco’s nidus theory failed to meet the 

reliability threshold under Rule 702 of the Federal Rules of 

Evidence. He also held that Dr. Hyman was not qualified to 

offer an opinion about medical causation and that the plaintiffs’ failure to disclose Dr. Kohr as an expert precluded

them from calling him to testify in that capacity. That left the 

plaintiffs without a causation expert—a requirement to 
8 No. 17-2068

prove the element of medical causation under Indiana law—

so the judge entered summary judgment for Bard.

II. Discussion

We normally review a summary judgment de novo, but 

our review is “slightly more nuanced” when summary 

judgment follows from a decision to exclude expert testimony. Higgins v. Koch Dev. Corp., 794 F.3d 697, 701 (7th Cir. 

2015). Our first question is whether the judge properly 

applied the Daubert framework for evaluating the admissibility of expert testimony. Id. (citing Daubert v. Merrell Dow 

Pharm., Inc., 509 U.S. 579 (1993)). We then review for abuse of 

discretion the judge’s decision to exclude the expert witness.

Id.

The plaintiffs must establish causation to prove a violation of the Indiana Products Liability Act. IND. CODE § 34-20-

1-1. Under Indiana law “questions of medical causation of a 

particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons 

learned in such matters.” Higgins, 794 F.3d at 703 (quoting 

Armstrong v. Cerestar USA, Inc., 775 N.E.2d 360, 366 (Ind. Ct. 

App. 2002)). “[W]hen there is no obvious origin to an injury 

and it has multiple potential etiologies, expert testimony is 

necessary to establish causation.” Id. (quotation marks

omitted).

The key expert testimony is that of Dr. Ferzoco; without 

it the plaintiffs cannot establish medical causation. They 

concede as much. They do not challenge the exclusion of 

Dr. Kohr as an expert based on their procedural violation,

and they acknowledge that Dr. Hyman’s opinion “does not, 

in and of itself, establish medical causation.” We therefore 
No. 17-2068 9

focus our attention on the exclusion of Dr. Ferzoco’s testimony under Rule 702.

An expert’s opinion is permitted 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.

FED. R. EVID. 702.

The familiar Daubert two-step framework applies to determine whether the requirements of Rule 702 have been 

satisfied. 509 U.S. at 593–94. The proponent of the expert 

testimony must first establish that “the proposed witness 

would testify to valid scientific, technical, or other specialized knowledge.” Ammons v. Aramark Unif. Servs., Inc., 

368 F.3d 809, 816 (7th Cir. 2004) (internal quotation marks

omitted). The proponent must then show that the expert 

testimony will assist the trier of fact. Id. At step one the 

judge evaluates whether the expert’s theory has been 

“(1) tested, (2) subjected to peer review and publication, 

(3) analyzed for known or potential error rate, and/or is 

(4) generally accepted within the specific scientific field.” 

Lapsley v. Xtek, Inc., 689 F.3d 802, 810 (7th Cir. 2012). At step 

two the judge evaluates “whether the proposed scientific 
10 No. 17-2068

testimony fits the issue to which the expert is testifying.” 

United States v. Hall, 165 F.3d 1095, 1102 (7th Cir. 1999).

The judge properly applied the Rule 702 and Daubert

standards in addressing Bard’s motion. He summarized 

Dr. Ferzoco’s theory that the patch buckled and rubbed 

against Mrs. Bowersock’s colon, causing fecal matter to 

escape through an opening that either closed prior to discovery or was not visible to the naked eye. He then explained why this novel theory of causation wasn’t reliable. 

To begin, the theory wasn’t tested, subjected to peer review, 

or described in medical literature. See Lapsley, 689 F.3d at

810. Moreover, the phenomena that Dr. Ferzoco described 

were not found in Mrs. Bowersock’s medical records or 

autopsy report. Last, the judge discounted Dr. Ferzoco’s

contention that he had previously treated patients injured in 

this manner, explaining that the claim was not substantiated

with identified patients or records. See Olinger v. U.S. Golf 

Ass’n, 52 F. Supp. 2d 947, 950 (N.D. Ind. 1999) (“The court 

cannot evaluate the reliability of the undisclosed methodology or of the principles that support the methodology.”). 

On appeal the plaintiffs contend that Dr. Ferzoco’s method was the equivalent of a differential diagnosis, which is an 

“accepted and valid methodology.” Myers v. Ill. Cent. R.R. 

Co., 629 F.3d 639, 644 (7th Cir. 2010). Put in simple terms, a 

differential diagnosis “provides a framework in which all 

reasonable hypotheses are ‘ruled in’ as possible causes of a 

medical problem and some of these possible causes are then 

‘ruled out’ to the extent scientific evidence makes it appropriate to do so.” Ervin v. Johnson & Johnson, Inc., 492 F.3d 901, 

903 (7th Cir. 2007). The plaintiffs didn’t raise this argument 

at summary judgment, however. They first used the term 
No. 17-2068 11

“differential diagnosis” in their motion to alter or amend the 

judgment. That’s too late to preserve an argument for appeal. Cf. Green v. Whiteco Indus., Inc., 17 F.3d 199, 201 n.4 (7th 

Cir. 1994) (“[R]aising [an] argument for the first time in the 

motion for reconsideration is not adequate to preserve the 

issue for appeal and definitively waives it.”).

The plaintiffs insist that they presented the argument below, just without using the term “differential diagnosis.”

They point to their argument at summary judgment that 

Dr. Ferzoco’s opinions were “founded on reliable methods, 

experience[,] and data.” That’s far too general a statement to 

situate their expert’s opinion in the specific domain of 

differential-diagnosis methodology. See Fednav Int’l Ltd. v. 

Cont’l Ins. Co., 624 F.3d 834, 841 (7th Cir. 2010) (explaining 

that the failure to present a specific argument below results 

in waiver, even if the argument “may have been before the 

district court in more general terms”). 

Even if preserved, the argument fails on the merits. 

Though differential diagnosis is widely accepted as a general 

matter, an expert’s decision to “rule in” or “rule out” potential causes must itself be “scientifically valid.” Ervin, 492 F.3d 

at 904. In other words, Dr. Ferzoco needed to establish the 

reliability of his nidus theory in order to “rule in” the buckling as a potential cause of Mrs. Bowersock’s death. As 

we’ve noted, the judge identified several reasons why 

Dr. Ferzoco’s nidus theory is not sufficiently reliable. 

The plaintiffs also argue that a scientific theory should 

not be rejected solely because it lacks peer review. See Smith 

v. Ford Motor Co., 215 F.3d 713, 720 (7th Cir. 2000). But the 

judge gave multiple reasons for his decision, including the 

lack of corroborating evidence in Mrs. Bowersock’s medical 
12 No. 17-2068

records and autopsy report. Along the same lines, the plaintiffs repeatedly assert that the lack of scientific literature 

supporting the expert’s theory goes to the weight, not the 

admissibility, of his testimony. That’s not the correct standard. Rule 702 and Daubert require the judge to act as a vigorous gatekeeper to ensure the reliability of expert testimony. 

See Kumho Tire Co. v. Carmichael, 526 U.S. 137, 149 (1999). 

In sum, the plaintiffs cannot prove medical causation 

without Dr. Ferzoco’s testimony. The record reflects that the 

judge properly applied the Daubert framework and soundly 

exercised his discretion to exclude it. It follows that Bard 

was entitled to summary judgment.

AFFIRMED.