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WO

IN THE UNITED STATES DISTRICT COURT

FOR THE DISTRICT OF ARIZONA

Arturo Contreras, individually; Jose N. 

Torres, individually,

Plaintiffs,

v. 

Chester David Brown; Legacy, Inc. and; 

Roe Business Entities I through X, 

inclusive,

Defendants.

No. CV-17-08217-PHX-JAT

ORDER 

Pending before the Court is Plaintiffs’ Motion to Strike Defendants’ Expert Mary 

Rossi (Doc. 122). The Court now rules on the motion. 

I. BACKGROUND

On February 21, 2019, Plaintiffs filed the pending Motion to Strike Defendants’ 

Expert Mary Rossi. (Doc. 122). Defendants subsequently filed a Response (Doc. 124) on 

March 7, 2019, to which Plaintiffs filed a Reply (Doc. 126) on March 13, 2019. 

A. Facts

The Court previously discussed the background facts of this case at length and 

need not repeat them here. (See Doc. 137 at 2). Relevant to the pending motion, Plaintiff 

Torres incurred significant medical bills from treatment in Arizona and Nevada following

a rear-end collision with Defendant Brown. (Doc. 122 at 2). Defendants retained Rossi as 

an expert to testify in the area of medical billing. (Doc. 124 at 1). Rossi holds a degree in 

nursing, is a registered nurse in Wisconsin, and became a certified legal nurse consultant 
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in 2004. (Doc. 124 at 4–5 (citing Doc. 124-6 at 2); see also Doc. 124-7 at 5). Rossi

previously testified in multiple venues across the country about the reasonable value of 

medical services. (Doc. 124 at 5 (citing Doc. 124-7 at 6)). Rossi is not, nor has she ever

been, licensed as a nurse in Arizona or Nevada. (Doc. 122 at 2; Doc. 124 at 5). 

II. LEGAL STANDARD 

A. Federal Rule of Evidence 702 and Daubert 

Rule 702 provides that: 

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.

Fed. R. Evid. 702.

The United States Supreme Court and the Ninth Circuit Court of Appeals issued 

opinions interpreting Rule 702 that guide this Court’s analysis. See Daubert v. Merrell 

Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993) (“Daubert I”); see also Daubert v. 

Merrell Dow Pharmaceuticals, 43 F.3d 1311 (9th Cir. 1995) (“Daubert II”). In Daubert 

I, the Supreme Court held that Rule 702 imposes a special gatekeeping obligation upon a 

trial judge to make a preliminary assessment of the admissibility of expert scientific 

testimony. Daubert I, 509 U.S. at 589. Specifically, the Supreme Court held that under 

Rule 702, “the trial judge must ensure that any and all scientific testimony or evidence 

admitted is not only relevant, but reliable.” Id. at 589. Whether the expert is appropriately 

qualified, whether her testimony is relevant, and whether her testimony is reliable are all 

distinct inquiries under Rule 702. See id. at 591; see also Mukhtar v. Cal. State Univ., 299 

F.3d 1053, 1066 (9th Cir. 2002) (indicating that reliability of an expert’s testimony is a 
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distinct inquiry from whether an expert is qualified).

1. Qualifications 

As an initial matter, the trial court must determine whether a proposed expert is 

qualified under Rule 702 by “knowledge, skill, experience, training, or education.”

Daubert I, 509 U.S. at 588 (citing Fed. R. Evid. 702); see also Daubert II, 43 F.3d at 

1315. Because the rule “contemplates a broad conception of expert qualifications,” only a 

“minimal foundation of knowledge, skill, and experience” is required. Wagner v. ABW 

Legacy Corp, Inc., No. CV–13–2245–PHX–JZB, 2016 WL 880371, at *5 (Mar. 8, 2016)

(citing Hangarter v. Provident Life & Accident Ins. Co., 373 F.3d 998, 1015–16 (9th Cir. 

2004)). A lack of particularized expertise “goes to the weight of the testimony, not its 

admissibility.” Id. (citing United States v. Garcia, 7 F.3d 885, 890 (9th Cir. 1993)).

2. Reliability 

Generally, to satisfy Rule 702’s reliability requirement, “the party presenting the 

expert must show that the expert’s findings are based on sound methodology.” Daubert 

II, 43 F.3d at 1316. Factors for a trial court to consider in determining reliability include: 

(1) whether the theory, technique, or method used by the expert to form her opinion can 

or has been tested; (2) the known or potential rate of error in the expert’s theory, 

technique, or method; (3) whether the theory, technique, or method has been subjected to 

peer review and publication; (4) whether there are standards controlling the theory, 

technique, or method’s operation; and (5) the general acceptance of the theory, technique 

or method within the relevant community. See Cooper v. Brown, 510 F.3d 870, 942–43 

(9th Cir. 2007) (citing Daubert I, 509 U.S. at 593–94); see also United States v. Prime, 

431 F.3d 1147, 1152 (9th Cir. 2005). 

The list is illustrative, not exhaustive, and may be inapplicable in a given case. 

Daubert II, 43 F.3d at 1317. As the Supreme Court recognized, all expert theories may 

not fit neatly into the five factors carved out in Daubert I and Daubert II; as such, the test 

for reliability must be “flexible.” Kumho Tire v. Carmichael, 526 U.S. 137, 141 (1999). 

This is especially so when the expert is testifying to “technical” or “other specialized 
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knowledge” as opposed to scientific testimony. Id. at 148 (citing Fed. R. Evid. 702). As 

such, a trial court may consider the enumerated factors, but ultimately must determine 

whether the testimony has a “reliable basis in the knowledge and experience of the 

relevant discipline.” Id. at 149 (citing Daubert I, 509 U.S. at 592).

3. Relevance and Fit 

Once qualified, an expert may testify within her area of expertise so long as the 

expert’s testimony “is both relevant and reliable.” Cooper, 510 F.3d at 942 (9th Cir. 

2007); see also Daubert I, 509 U.S. at 589. Expert testimony is relevant if it assists the 

trier of fact in understanding evidence or in determining a fact in issue. Daubert I, 509 

U.S. at 591. Thus, the party proffering such evidence must demonstrate a valid scientific 

connection, or “fit,” between the evidence and an issue in the case. Id. A court therefore 

examines whether the proffered expert testimony is “sufficiently tied to the facts of the 

case that it will aid the jury in resolving a factual dispute.” Id. (quoting United States v. 

Downing, 753 F.2d 1224, 1242 (3d Cir. 1985)). Expert knowledge also assists the trier of 

fact when it provides knowledge beyond the trier of fact’s common knowledge. Id.; 

United States v. Finley, 301 F.3d 1000, 1008 (9th Cir. 2002).

B. Collateral Source Rule

“Arizona follows the common law collateral source rule, which provides that 

payments made to or benefits conferred on the injured party from other sources are not 

credited against the tortfeasor’s liability, although they cover all or a part of the harm for 

which the tortfeasor is liable.” Mesirow v. Leiserv, Inc., No. CIV 04-2052 PHX RCB, 

2005 WL 6271135, at *4 (D. Ariz. Dec. 1, 2005) (internal quotation marks and citations 

omitted). “The collateral source rule is most often applied in cases where an injured party 

recovers from a tortfeasor amounts for which plaintiff has already been compensated by 

his insurer.” Lopez v. Safeway Stores, Inc., 129 P.3d 487, 492 (App. 2006). Arizona 

courts recognize that “[p]ayments made to a medical provider by an insurance carrier on 

behalf of an insured . . . are payments made by a collateral source and, thus, are not 

admissible in evidence for that reason.” Id. at 496 (citation omitted). 
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III. ANALYSIS 

Plaintiffs move to strike Defendants’ expert Rossi pursuant to Rule 702 and 

Daubert, as well as the collateral source rule. (See Doc. 122 at 3)

A. Federal Rule of Evidence 702 and Daubert 

Plaintiffs argue that the report and testimony of Defendants’ medical billing expert

are inadmissible under Rule 702 based on: (1) qualifications; (2) reliability; (3) relevance; 

and (4) the collateral source rule. (Doc. 122 at 5–8). The Court will address each 

argument in turn. 

1. Qualifications 

Plaintiffs first challenge Rossi’s professional qualifications. (See Doc. 122 at 5). 

Plaintiffs assert that Rossi, while a registered nurse and certified legal nurse consultant, 

“is not qualified to offer her opinions regarding whether the charges for Torres’ medical 

treatment was usual and customary for Las Vegas, Kingman, or Reno” because she is not 

licensed, nor has she practiced nursing in a medical setting, in Nevada or Arizona. (Id. at 

5–6). Defendants respond that “[a] billing expert is not required to be a licensed nurse,” 

so it is irrelevant where exactly Rossi is licensed or historically practiced. (Doc. 124 at 5).

Rossi also routinely testifies in jurisdictions outside of the state in which she holds her 

nursing license—Wisconsin—with only one instance of exclusion. (Doc. 122-1 at 57–59; 

124-7 at 6). The Court agrees with Defendants that Rossi’s experience in the medical 

field, and familiarity with billing practices nationally, provides a “minimal foundation” in 

her area of expertise. See Wagner, 2016 WL 880371, at *5 (citations omitted). Her lack 

of particularized expertise regarding Arizona and Nevada “goes to the weight of [her] 

testimony, not its admissibility.” Id. (citations omitted).

“As the Supreme Court explained in Daubert [I], 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.” 

Wichansky v. Zowine, No. CV-13-01208-PHX-DGC, 2016 WL 6818945, at *3–4 (D. 

Ariz. Mar. 22, 2016) (denying a motion to exclude a medical billing expert because her
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30 years of general experience in medical billing and past engagement by attorneys were

sufficient qualifications). Accordingly, the Court finds Rossi to be qualified to provide 

testimony regarding the reasonable value of the medical services received by Plaintiff 

Torres under Rule 702.

2. Reliability

Plaintiffs next argue that Rossi’s proffered testimony is unreliable because it is 

“derived exclusively from a third-party database whose information she has not verified.” 

(Doc. 122 at 5). Rossi provides that she relied on MCMC’s ZEBRA database—since 

rebranded as CareWorks—in forming her opinions of the reasonable value of medical 

services provided to Plaintiff Torres. (Doc. 124 at 6 (citing Doc. 124-7 at 7)). Rossi 

explains that the database compiles medical bills submitted for various Current 

Procedural Terminology (“CPT”) codes in discrete geographic regions.1 Defendants 

further provide that “[p]hysicians and facilities charge rates for procedures and products 

by submitting them under specific CPT codes,” such that each CPT code corresponds to a 

particular medical service. (Id. at 7). Per her methodology, Rossi then uses the database, 

along with her experience in the medical billing field, to assess the accuracy and 

reasonableness of charges associated with each CPT code provided in the treatment of 

Plaintiff Torres. (Id.). 

Rule 703 provides that “[a]n expert may base an opinion on facts or data in the 

case that the expert has been made aware of or personally observed.” Fed. R. Evid. 703. 

Thus, “[i]f experts in the particular field would reasonably rely on those kinds of facts or 

data in forming an opinion on the subject, they need not be admissible for the opinion to 

be admitted.” Id. Arizona courts provide that a “negligence plaintiff cannot rely only on 

medical records and bills to show medical expenses were necessary and reasonable; other 

evidence must establish the latter.” Larsen v. Decker, 995 P.2d 281, 286 (Ariz. Ct. App. 

 

1

“CPT medical billing codes are assigned by the American Medical Association 

to various medical services for the purpose of communicating uniform information about 

medical services and procedures.” Mathis v. Milgard Mfg., Inc., No. 3:16-CV-02914-

BEN-JLB, 2019 WL 482490, at *2 (S.D. Cal. Feb. 7, 2019).
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2000), amended (Feb. 22, 2000). It stands to reason, therefore, that experts may rely on 

industry standards and comparison data sources to establish the reasonableness of 

medical bills in a particular instance. Defendants assert, and Plaintiffs do not refute, that 

Rossi “follows the guidelines established by the American Medical Association with 

respect to CPT coding”—the standard industry practice—in her assessment. (Doc. 124 at 

7).

Plaintiffs question the sample size and reliability of inputs (medical bills) for the 

database used by Rossi. (See Doc. 122 at 6). Plaintiffs, however, do not establish that the 

database includes inaccurate medical bills, mismatched CPT codes, or that the sample 

size of bills in the relevant regions are insufficient to provide fair estimates of reasonable 

medical charges for the services provided to Plaintiff Torres. (Compare id. with Doc. 124 

at 7). Consistent with other courts, this Court agrees with Defendants “that the costing 

associated with CPT codes is standardized in the medical billing industry and something 

[Rossi] could reasonably rely upon.” Mathis, 2019 WL 482490, at *1–2 (denying a 

motion to strike expert testimony pertaining to medical costs when the expert used a data 

source “to identify reasonable billing values for the CPT codes” submitted by the treating 

physician). To the extent Plaintiffs wish to scrutinize the bases for Rossi’s opinions, 

“[Plaintiffs] can test those opinions at trial on cross-examination.” See id. Accordingly, 

the Court finds Rossi’s proffered testimony sufficiently reliable under Rule 702. 

3. Relevance and Fit 

Finally, Plaintiffs challenge the relevance of Rossi’s testimony. (Doc. 122 at 6). 

Plaintiffs argue that the proffered testimony is irrelevant because Rossi’s estimates of 

reasonable charges for the services provided herein are not based on an adequate 

understanding of customary charges in the relevant regions, nor “the result of any 

experience or specialized training.” (Id.). Although couched under the issue of relevance, 

Plaintiffs arguments again go to the reliability of Rossi’s methodologies and underlying 

data source. (Compare id. at 6 with Doc. 126 at 3–4). Based on the above reasoning, this

Court determined that Rossi’s methods are sufficiently reliable under Rule 702. See supra 
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Part III(A)(2). Assuming Plaintiffs can lay proper foundation for Rossi’s analysis, the 

reasonable cost of medical charges incurred by Plaintiffs will assist the trier of fact in 

analyzing the disputed issue of damages. See Daubert I, 509 U.S. at 591. Accordingly, 

the Court finds that Rossi’s proffered testimony is relevant to the facts of the case, thus 

satisfying Rule 702.

2

B. Collateral Source Rule

Additionally, Plaintiffs argue that this Court should “bar [] Rossi’s testimony 

because it violates the collateral source rule.” (Doc. 122 at 8). Specifically, Plaintiffs 

contend that “[d]iscussion of health insurance reimbursement . . . is clearly collateral 

source evidence.” (Id.). Conversely, Defendants avow that “Rossi is not introducing 

evidence that Plaintiff[s] received any sort of insurance coverage or benefit from an 

alternative source.” (Doc. 124 at 8). 

As Plaintiffs point out, “Arizona law allows Plaintiffs to claim and recover the full 

amount of reasonable medical expenses charged.” (Doc. 126 at 4 (citing Lopez, 129 P.3d 

at 496 (holding that the plaintiff “was entitled to claim and recover the full amount of her 

reasonable medical expenses for which she was charged” (emphasis added))). Here, 

Defendants purport to offer Rossi’s report and testimony regarding customary medical 

charges to challenge the reasonableness of medical expenses incurred by Plaintiff Torres. 

(See Doc. 124 at 8). Courts in other jurisdictions that utilize the common law collateral 

source rule generally allow precisely this type of evidence to be introduced for this 

particular purpose. See, e.g., Aquino v. Watts, No. 1:11-CV-212, 2014 WL 2208183, at 

*2 (D. Vt. May 28, 2014) (“[Defendants] may, however, introduce any relevant evidence 

of the reasonable value of medical services that is not barred by the collateral source rule. 

This may include, for example, evidence as to what the provider usually charges for the 

 

2 Plaintiffs also contend that Rossi “opines on the medical necessity of [Plaintiff] 

Torres’ care, despite not being qualified as a medical doctor.” (Doc. 122 at 6). Plaintiffs 

do not support this assertion with a citation, and Defendants further provide that Rossi’s 

testimony is confined to the charges related to Plaintiff Torres’ treatment. (See generally 

Doc. 124). If Defendants attempt to solicit testimony beyond the scope of Rossi’s report 

or qualifications, Plaintiffs may raise the appropriate objection at trial.
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services provided, or what other providers usually charge.” (citation omitted)); Reed v. 

Nat’l Council of Boy Scouts of Am., Inc., 706 F. Supp. 2d 180, 194 (D.N.H. 2010) 

(reasoning that New Hampshire’s collateral source rule does not bar a defendant from 

“questioning the face amounts of the medical bills as equivalent to the reasonable value 

of [a plaintiff’s] medical services” (citation omitted)). Without the full context available 

at trial, the Court cannot determine that Rossi’s proffered testimony would necessarily 

discuss inadmissible insurance coverage or related benefits received by Plaintiff Torres at 

this stage. Accordingly, Plaintiffs motion on the basis of the collateral source rule is 

likewise denied.

IV. CONCLUSION 

Based on the foregoing, 

IT IS ORDERED that the Plaintiffs’ Motion to Strike Defendants’ Expert Mary 

Rossi (Doc. 122) is DENIED. 

Dated this 10th day of May, 2019.