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Certiorari Granted, December 3, 2010, No. 32,690

IN THE COURT OF APPEALS OF THE STATE OF NEW MEXICO

Opinion Number: 2010-NMCA-110

Filing Date: October 6, 2010

Docket No. 29,120 

JOEY PARKHILL and PAULA PARKHILL,

a married couple, on their own behalf and on 

behalf of their minor children, VICTORIA 

PARKHILL and REBEKAH PARKHILL,

Plaintiffs-Appellants,

v.

ALDERMAN-CAVE MILLING AND 

GRAIN COMPANY OF NEW MEXICO,

Defendant-Appellee.

APPEAL FROM THE DISTRICT COURT OF GRANT COUNTY

Kevin R. Sweazea, District Judge

Laurence M. Berlin

Reserve, NM 

Moriarty, Badaruddin & Booke

Bradley L. Booke

Missoula, MT

for Appellants

Atkinson, Thal & Baker, P.C.

John S. Thal

Clifford K. Atkinson

Elizabeth Losee

Albuquerque, NM 

for Appellee
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OPINION

VANZI, Judge.

{1} This is an appeal from the district court’s decisions excluding the opinion testimony

of Plaintiffs’ two expert witnesses as to the cause of their medical conditions. Plaintiff Joey

Parkhill also appeals a discovery-related ruling in which the district court dismissed his

personal injury claims as a sanction for discovery abuses. For the reasons discussed below,

we conclude that the district court did not err in excluding Plaintiffs’ medical experts’

causation testimony. Because we affirm the district court’s ruling on the expert witnesses,

we need not reach Plaintiff’s sanction issue. 

BACKGROUND

{2} Plaintiffs Joey and Paula Parkhill along with their two minor children (collectively,

the Parkhills) operate several horse ranches located in southern New Mexico. Defendant

Alderman-Cave Milling and Grain Company of New Mexico (ACMG) produces and

markets horse feed in New Mexico. 

{3} In April 2004, Joey Parkhill purchased eighty fifty-pound sacks (two tons) of ACMG

horse feed. Mr. Parkhill distributed half of the horse feed to two ranches located in Dexter,

New Mexico, delivering five bags to one ranch and thirty-five bags to the other. Mr.

Parkhill took the remaining forty sacks of feed to his home ranch in Lordsburg, New

Mexico. 

{4} Over the course of the two weeks following Mr. Parkhill’s purchase, the Parkhills

fed the ACMG horse feed twice daily to the horses at the Lordsburg location. Three workers

at the Dexter locations fed the ACMG horse feed twice daily to the horses at those locations.

Between mid-April 2004, when the Parkhills began feeding the ACMG feed, and May 1,

2004, when the use of the ACMG feed was discontinued at all locations, several horses from

all locations became sick and died. Additionally, the Parkhills claim that several mares

spontaneously aborted. 

{5} While investigating the deaths of the horses, the New Mexico Department of

Agriculture took a number of samples of the feed. Testing showed that the samples

contained small amounts of monensin, an antibiotic that is a common additive to livestock

feed but is known to be toxic to horses and is, therefore, prohibited in horse feed. One

sample of the horse feed contained 8 grams of monensin per ton and another sample

contained 3 grams of monensin per ton. The remaining samples appear to have contained

less than 2.3 grams of monensin per ton. 

{6} The Parkhills allege that they experienced a number of physical symptoms within

days after they started feeding their horses the ACMG feed and that their symptoms are

related to their contact with the feed. The Parkhills claim that their symptoms included skin

rashes, irritated eyes, brittle nails, and diarrhea. It does not appear from the record that any

of the Parkhills sought medical treatment for their symptoms at the time of their contact with
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the ACMG feed. On June 30, 2004, approximately ten weeks after the horse feed had first

been used, and approximately eight weeks after the feed was discontinued, Mr. Parkhill

sought treatment from his doctor, Gregory Koury, M.D., for pain in his left shoulder related

to Mr. Parkhill having recently been hit by a bull. Subsequently, both Mr. and Mrs. Parkhill

and their two daughters saw Dr. Koury for a variety of generalized health complaints:

including dizziness and light-headedness, breathing difficulties, insomnia, decreased energy,

irritability, elevated blood pressure, and weight gain. The three workers at the Dexter

location did not report any adverse physical symptoms related to their contact with the horse

feed. 

{7} The Parkhills sought to have their treating physician, Dr. Koury, and another doctor,

James Dahlgren, M.D., testify as experts on causation. Specifically, Dr. Koury and Dr.

Dahlgren would testify that, to a reasonable degree of medical probability, the various health

problems the Parkhills suffered since their contact with the ACMG horse feed in 2004 were

caused by the Parkhills’ exposure to monensin contained in the feed. ACMG filed a motion

in limine to exclude both Dr. Koury’s and Dr. Dahlgren’s testimony. The district court held

a two-day evidentiary hearing on the motion, during which several experts from both sides

testified at length. The district court found that the testimony of both Dr. Koury and Dr.

Dahlgren was not reliable, would not assist the trier of fact, and should, therefore, be

excluded. 

{8} The parties settled their claims with respect to the horses on October 10, 2008, and

the district court subsequently entered a final judgment dismissing those claims with

prejudice. In the settlement agreement, however, the Parkhills reserved their right to pursue

claims for damages related to their personal health, and these claims are the basis of this

appeal. 

{9} On appeal, the Parkhills assert that the district court abused its discretion when the

court excluded Dr. Dahlgren from testifying that, to a reasonable degree of medical certainty,

exposure to monensin caused the Parkhills’ physical symptoms. The Parkhills also contend

that the district court erred by limiting Dr. Koury’s testimony to his care and treatment of

the Parkhills. We discuss each of the Parkhills’ assertions in turn. 

DISCUSSION

New Mexico Law Regarding the Admission/Exclusion of Expert Testimony

{10} We begin our discussion with a brief review of New Mexico law regarding the

admission/exclusion of expert testimony. Admission or exclusion of expert testimony in

New Mexico is governed by Rule 11-702 NMRA, which states:

If scientific, technical or other specialized knowledge will assist the

trier of fact to understand the evidence or to determine a fact in issue, a

witness qualified as an expert by knowledge, skill, experience, training or

education may testify thereto in the form of an opinion or otherwise.
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{11} In State v. Alberico, 116 N.M. 156, 166, 861 P.2d 192, 202 (1993), the New Mexico

Supreme Court explained that Rule 11-702 establishes three prerequisites for admission of

expert testimony: “(1) experts must be qualified; (2) their testimony must assist the trier of

fact; and (3) their testimony must be limited to the area of scientific, technical, or other

specialized knowledge in which they are qualified.” State v. Torres, 1999-NMSC-010, ¶ 23,

127 N.M. 20, 976 P.2d 20. 

{12} Pursuant to Rule 11-702, the district court is required to act as a “gatekeeper” to

ensure that an expert’s testimony rests on both a reliable foundation and is relevant to the

task at hand so that speculative and unfounded opinions do not reach the jury. State v.

Downey, 2008-NMSC-061, ¶ 25, 145 N.M. 232, 195 P.3d 1244.

{13} In addition to the evidentiary reliability standard in Rule 11-702, the Alberico Court

adopted the United States Supreme Court holding in Daubert v. Merrell Dow

Pharmaceuticals, Inc., 509 U.S. 579 (1993), establishing that it is an “error to admit expert

testimony involving scientific knowledge unless the party offering such testimony first

establishes the evidentiary reliability of the scientific knowledge.” Torres, 1999-NMSC010, ¶ 24. “[I]n New Mexico, evidentiary reliability is the hallmark for the admissibility of

scientific knowledge.” Id. ¶ 26. “[U]nder the Rules of Evidence the trial judge must ensure

that any and all scientific testimony or evidence admitted is not only relevant, but reliable.”

Id. ¶ 25 (alteration omitted) (internal quotation marks and citation omitted).

{14} More recently, in Torres, our Supreme Court reasserted that New Mexico courts

should apply the factors defined by the United States Supreme Court in Daubert when

considering scientific testimony. The Court stated that

in considering the reliability of any particular type of scientific knowledge,

the trial court should consider the following factors: 

(1) whether a theory or technique can be (and has been)

tested; (2) whether the theory or technique has been subjected

to peer review and publication; (3) the known or potential rate

of error in using a particular scientific technique and the

existence and maintenance of standards controlling the

technique’s operation; (4) whether the theory or technique has

been generally accepted in the particular scientific field.

Torres, 1999-NMSC-010, ¶ 25 (alteration omitted) (internal quotation marks and citation

omitted). New Mexico courts rely upon the Daubert factors, along with a fifth factor:

“whether the scientific technique . . . is capable of supporting opinions based upon

reasonable probability rather than conjecture.” State v. Anderson, 118 N.M. 284, 291, 881

P.2d 29, 36 (1994) (internal quotation marks and citation omitted).

{15} Subsequent federal cases, such as Kumho Tire Co. v. Carmichael, 526 U.S. 147, 138

(1999), have gone further and required that all expert testimony, not just scientific testimony,

be subject to the Daubert-Alberico standard. New Mexico courts have not adopted this

requirement; rather, “New Mexico law requires only that the trial court establish the
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reliability of scientific knowledge, and does not apply the Daubert-Alberico standard to all

expert testimony.” State v. Lente, 2005-NMCA-111, ¶ 4, 138 N.M. 312, 119 P.3d 737. With

this guidance, we address the Parkhills’ claims. 

Standard of Review

{16} Both parties agree that the appropriate standard of review for the district court’s

decision regarding the admission of expert testimony is abuse of discretion. “[T]he

admission of expert testimony or other scientific evidence is peculiarly within the sound

discretion of the trial court and will not be reversed absent a showing of abuse of that

discretion.” Alberico, 116 N.M. at 169, 861 P.2d at 205. “An abuse of discretion occurs

when a ruling is clearly contrary to the logical conclusions demanded by the facts and

circumstances of the case.” Sims v. Sims, 1996-NMSC-078, ¶ 65, 122 N.M. 618, 930 P.2d

153.

{17} Additionally, the Parkhills argue that the district court erred as a matter of law by

applying the Daubert-Alberico evidentiary standard to Dr. Koury’s testimony because Dr.

Koury did not—and was not required to—rely on scientific knowledge for his opinion. As

our Supreme Court stated in Torres, “the initial determination of whether to apply the

[Daubert-Alberico] standard entails a conclusion of law that is subject to de novo review.”

Torres, 1999-NMSC-010, ¶ 28. We therefore review de novo the district court’s decision

to apply the Daubert-Alberico standard to the portions of Dr. Koury’s testimony that the

court found required scientific knowledge. We then review the district court’s decision to

exclude Dr. Koury’s and Dr. Dahlgren’s expert testimony for an abuse of discretion.

Daubert-Alberico Applies to Dr. Koury’s Testimony

{18} The Parkhills contend that the district court erred in limiting the testimony of Dr.

Koury within the unique context of this toxic tort. They assert that Dr. Koury properly

applied a differential diagnosis to determine the cause of the Parkhills’ symptoms and that

because Dr. Koury was the Parkhills’ treating physician, he was qualified as an expert to

give his opinion as to causation in this case. The Parkhills further argue that Dr. Koury’s

opinion should not have been subjected to a Daubert-Alberico analysis because it was based

on Dr. Koury’s experience and training, not on scientific knowledge. 

{19} In support of their position, the Parkhills cite Banks v. IMC Kalium Carlsbad Potash

Co., 2003-NMSC-026, ¶ 22, 134 N.M. 421, 77 P.3d 1014, which states that “[a] treating

physician is uniquely qualified to give an opinion about his or her diagnosis of a patient and

the admissibility of such testimony should be given due deference.” In Banks, our Supreme

Court went on to say that “[a] treating physician’s testimony is based more on experience

and training than on the kind of scientific knowledge to which New Mexico courts apply

Daubert-Alberico.” Id. (internal quotation marks and citation omitted). While the Parkhills

accurately cite to Banks, we find that case distinguishable. In Banks, the Court found that

the Daubert-Alberico requirements of showing evidentiary reliability of scientific evidence

was not applicable under the particular provisions of NMSA 1978, Section 52-1-28(B)

(1987) of the Workers’ Compensation Act. Banks, 2003-NMSC-026, ¶ 11. The Court has
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not had the opportunity to address the issue in a context outside of the Workers’

Compensation Act.

{20} In this case, the district court determined that Dr. Koury was qualified in his capacity

as the Parkhills’ treating physician to testify as to his differential diagnosis of the internal

causes of the Parkhills’ symptoms, e.g., Mr. Parkhill’s obesity is a cause of his hypertension.

The district court concluded that because Dr. Koury’s testimony as to internal causation was

based on his experience and training, rather than scientific knowledge, the testimony was not

required to meet the Daubert-Alberico evidentiary standard. The district court noted,

however, that in addition to testifying as to internal causation, the Parkhills also sought to

have Dr. Koury testify to the external cause of their symptoms, i.e., that, to a reasonable

degree of medical probability, the Parkhills’ symptoms were caused by their exposure to

monensin. The district court ruled that testimony as to external causation, or etiology, was

beyond the expertise of the average treating physician and beyond the scope of a differential

diagnosis conducted for the purposes of diagnosis and treatment. The district court ruled

that testimony as to external causation required specific scientific knowledge and, therefore,

such testimony must meet the Daubert-Alberico evidentiary standard. We agree.

{21} We conclude that the Parkhills’ argument for the admissibility of Dr. Koury’s overall

testimony conflates the determination of the disease that is the cause of a patient’s

symptoms, which might be determined by applying a differential diagnosis, with the

determination of the external cause of the disease itself which, as in the case before us, often

requires a rigorous scientific analysis of the various external agents that might have caused

the disease. 

{22} We find the Eleventh Circuit Court of Appeals’ discussion of the distinction between

the determination of the disease and a determination of the external causation of the disease

in McClain v. Metabolife International, Inc., 401 F.3d 1233, 1236 (11th Cir. 2005), to be

instructive in this regard. At the outset, we note that in McClain, the Court of Appeals

acknowledged that a differential diagnosis approach may offer an important component of

a valid methodology and can satisfy a Daubert analysis if the expert can show the general

toxicity of the drug by reliable methods. Id. at 1252-53. The Court explained that a

“[d]ifferential diagnosis involves ‘the determination of which one of two or more diseases

or conditions a patient is suffering from, by systematically comparing and contrasting their

clinical findings.’” Id. at 1252 (quoting Dorland’s Illustrated Medical Dictionary 240

(Douglas M. Anderson et al. ed., 29th ed. 2000)). The Court went on to elucidate that this

methodology leads to “the diagnosis of the patient’s condition, not necessarily the cause of

that condition.” McClain, 401 F.3d at 1252 (citing Mary Sue Henifin et al., Reference

Manual On Scientific Evidence 439, 481 (Fed. Jud. Ctr. 2d ed. 2000)). The Court noted that

“[t]he more precise but rarely used term is differential etiology, which is a term used on

occasion by expert witnesses or courts to describe the investigation and reasoning that leads

to the determination of external causation.” McClain, 401 F.3d at 1252 (internal quotation

marks and citation omitted). See also Ian S. Spechler, Physicians at the Gates of Daubert:

A Look at the Admissibility of Differential Diagnosis Testimony to Show External Causation

in Toxic Tort Litigation, 26 Rev. Litig. 739, 743 (2007) (stating that a “[d]ifferential

diagnosis refers to the clinical process by which doctors determine the internal disease that
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is causing a patient’s suffering; differential etiology is used for determining the external

causes of the problems. In a differential diagnosis, a doctor isolates a disease that is causing

the patient’s symptoms, whereas differential etiology isolates an external factor that has

caused the internal disease.” (footnote omitted)); Edward J. Imwinkelried, The Admissibility

and Legal Sufficiency of Testimony About Differential Diagnosis (Etiology): Of Under—and

Over—Estimations, 56 Baylor L. Rev. 391, 402 (2004) (“If the key question is the cause of

the illness rather than the nature of the illness, the physician uses a related, but distinct

technique, that is, differential etiology.”); David L. Faigman, Symposium: The Role of the

Judge in the Twenty-First Century, Judges as “Amateur Scientists,” 86 B.U. L. Rev. 1207,

1221 (2006) (“Properly understood, differential diagnosis refers to the identification of the

illness or behavioral condition that a person is experiencing. Differential etiology refers to

the cause or causes of that condition.” (footnotes omitted)).

{23} As our Supreme Court has declared, a treating physician in a workers’ compensation

case is uniquely qualified to give an opinion regarding his or her diagnosis of the disease

causing the patient’s symptoms. Banks, 2003-NMSC-026, ¶ 22. Even if we extend the

Court’s ruling in Banks to cases outside the workers’ compensation context, we nevertheless

conclude that a treating physician is not automatically qualified to testify as to the external

agent that caused the patient’s disease. We acknowledge that, in some circumstances, the

use of a differential diagnosis can be a legitimate means of proving causation when the

treating physician can determine with some degree of certainty the external cause of a

patient’s disease as part of the diagnosis and treatment process. For example, a physician

may testify that the patient’s broken leg was caused by the patient falling off of a roof. On

the other hand, in many cases, including toxic tort cases like the one before us, the

determination of the external cause of a patient’s disease is a complex process that is

unrelated to diagnosis and treatment, and which requires specialized scientific knowledge

regarding the external agents involved. In such situations, a treating physician’s expert

opinion on causation is subject to the same standards of scientific reliability that govern the

expert opinions of physicians who are hired only for the purposes of litigation.

{24} We conclude that in order for Dr. Koury to testify as to external causation of the

Parkhills’ symptoms, i.e., that monensin caused those symptoms, Dr. Koury’s testimony

must be found to be reliable under the Daubert-Alberico evidentiary standard. Therefore,

we determine that, as a matter of law, the district court applied the appropriate evidentiary

standards to the two separate aspects of Dr. Koury’s testimony. 

Exclusion of Dr. Koury’s Testimony as to External Causation

{25} Having conducted a de novo review and determined that the district court properly

applied the Daubert-Alberico evidentiary standard to the parts of Dr. Koury’s testimony that

require scientific knowledge, we now review the district court’s exclusion of that testimony

for an abuse of discretion. 

{26} The district court determined that testimony as to the external causation of the

Parkhills’ symptoms required specific scientific knowledge that Dr. Koury did not possess.

The court found that Dr. Koury was not qualified to “render a reliable opinion on the subject
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[of] whether monensin was the external cause or etiology of the Plaintiffs’ medical

symptoms” because he lacked the background, training, and experience required for such

testimony. Additionally, the court found that Dr. Koury had not performed adequate

research or analysis to acquire the information necessary to render a reliable opinion.

Finally, the court found that Dr. Koury based his analysis on an assumption, which has no

scientific basis, i.e., that monensin stays permanently in the human body. The district court

concluded that this faulty assumption further rendered Dr. Koury unqualified to testify

regarding monensin’s effect on the Parkhills. 

{27} The Parkhills argue that the district court erred in excluding Dr. Koury’s testimony

based on his qualifications. The Parkhills assert that no specialized training or experience,

beyond being a medical doctor, is necessary for Dr. Koury to meet the first prerequisite for

admission of expert testimony defined by our Supreme Court, i.e., that experts must be

qualified. We disagree and conclude that a treating physician does not establish the

reliability of his techniques or the validity of his conclusions simply by claiming he

performed a differential diagnosis on a patient. 

{28} New Mexico law is clear that “a witness must qualify as an expert in the field for

which his or her testimony is offered before such testimony is admissible.” Downey, 2008-

NMSC-061, ¶ 26 (internal quotation marks and citation omitted). Additionally, broad

discretion is intentionally given to the trial court “to determine whether expert testimony will

assist the trier of fact.” Id. “In determining whether an expert witness is competent or

qualified to testify, the trial court has wide discretion.” Lopez v. Reddy, 2005-NMCA-054,

¶ 14, 137 N.M. 554, 113 P.3d 377 (alteration omitted) (internal quotation marks and citation

omitted). “The qualifications of an expert are dependent on the type of negligence claimed

and the medical complexity involved.” Id. ¶ 16. 

{29} At the Daubert hearing, Dr. Koury stated his qualifications as follows: that he holds

a medical degree from the University of New Mexico and is licensed to practice medicine

in New Mexico; that he currently practices family medicine in Silver City, New Mexico, but

is not board certified in family practice; that his only training related to toxicology was in

two classes taken in medical school, pharmacology and biochemistry, and that neither class

had any specific information regarding toxicology. Dr. Koury further testified that he did

not consider himself to be an expert in toxicology by education, training, or experience. 

{30} Specifically regarding monensin, Dr. Koury stated that he had not heard of the

substance prior to meeting the Parkhills and that the bulk of his information regarding

monensin came from the Parkhills. Dr. Koury also stated that he does not know how

monensin is handled when it is fed to cattle, what constitutes the minimum harmful dose for

a human being, or what constitutes the minimum harmful dose for an animal. Additionally,

Dr. Koury stated that he had not consulted with any experts on the subject of monensin and

that his opinions regarding monensin and its association with the Parkhills’ symptoms are

based exclusively on his examination of the Parkhills and his own research. Finally, Dr.

Koury testified that he was of the opinion that monensin is not eliminated from the body, but

rather stays in the body, even though he had no factual or experiential basis for that opinion,

and there was expert testimony stating that monensin is excreted from the body very rapidly.
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{31} Based on this testimony and a review of all written information submitted by the

parties, the district court determined that Dr. Koury’s differential diagnosis methodology was

not scientifically reliable, and he was therefore not qualified to offer an expert opinion that

required scientific knowledge of the properties, handling, and use of monensin. We

conclude that substantial evidence supported the exercise of the district court’s discretion

to limit the testimony of Dr. Koury and to exclude his medical opinion as to causation. We

affirm the district court’s decision.

Exclusion of Dr. Dahlgren’s Expert Testimony

{32} The Parkhills also proffered Dr. Dahlgren as an expert in environmental medicine

and toxicology to testify that the Parkhills’ illnesses were caused by their exposure to

monensin. It is unclear from the record whether the district court found Dr. Dahlgren to be

qualified to give his opinion that, to a reasonable degree of medical probability, the

Parkhills’ health symptoms were caused by their exposure to monensin. The court merely

stated that it found his qualifications to be “less than stellar.” The district court did,

however, find that Dr. Dahlgren’s testimony would not assist the trier of fact, as required by

the second prerequisite defined by our Supreme Court in Alberico, because the testimony

was not reliable under the Daubert-Alberico standard for scientific evidence. We agree with

the district court that Dr. Dahlgren’s testimony was not reliable under the Daubert-Alberico

standard.

{33} The district court found that under the rules of Daubert-Alberico, Dr. Dahlgren’s

methodology had not been tested or peer reviewed. The district court further found that the

methodology did not provide an estimate of the probability of error and that the doctor had

not quantified a dose of the presumed toxic agent, monensin, as the basis for his opinion.

Finally, the court noted Dr. Dahlgren’s utter lack of familiarity with monensin and the

manner in which the compound is used and handled in the industry. Based on these factors,

the court determined that Dr. Dahlgren’s opinion was unreliable and, therefore, inadmissible.

{34} The court reached its decision after a two-day evidentiary hearing during which the

court heard testimony from five experts: Dr. Koury, specializing in family medicine; Dr.

Dahlgren, specializing in internal medicine; Dr. Oehme, D.V.M., professor of toxicology at

the Kansas State University Veterinary College; Dr. Fisher, board certified in toxicology;

and Keith Behnke, Ph.D., professor of feed science at Kansas State University. 

{35} The Parkhills do not address the reliability of Dr. Dahlgren’s methodology— a

differential diagnosis—for determining external causation of the Parkhills’ symptoms in

accordance with the Daubert-Alberico factors cited by the district court. Instead, the

Parkhills cite a number of cases from other jurisdictions in which courts have found that a

properly employed differential diagnosis is a scientifically reliable methodology. The

Parkhills argue that based on these cases, a general acceptance of the differential diagnosis

methodology can be inferred. The Parkhills offer no other argument or evidence that a

differential diagnosis is a scientifically reliable methodology for determining external

causation. However, our Supreme Court concluded in Alberico and reiterated in Torres, “[i]t

is improper to look for scientific acceptance only from reported case law.” Alberico, 116
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N.M. at 167, 861 P.2d at 203; Torres, 1999-NMSC-010, ¶ 38. The policy behind our

Supreme Court’s decision in Alberico is to “allow a trial court to admit evidence of scientific

knowledge that is adequately valid (from a scientific viewpoint) to be sufficiently reliable

(from an evidentiary viewpoint).” Torres, 1999-NMSC-010, ¶ 39. 

{36} Consequently, as we have noted above, we do not believe that the Parkhills have

established that a differential diagnosis is the proper methodology for determining external

causation in this case. Even if we were to assume a properly applied differential diagnosis

to be an acceptable method for determining the external cause of the Parkhills’ symptoms,

the district court had to also determine that Dr. Dahlgren reliably applied that methodology

to the facts of the present case. In Downey, our Supreme Court reiterated that expert

testimony is only admissible under Rule 11-702 if it will assist the trier of fact, i.e., the

expert testimony must be relevant. Downey, 2008-NMSC-061, ¶ 30. “One aspect of

relevance is whether expert testimony proffered in the case is sufficiently tied to the facts

of the case that it will aid the jury in resolving a factual dispute.” Id. (internal quotation

marks and citation omitted). “The primary inquiry is whether the scientific methodology

‘fits’ the facts of the case and thereby proves what it purports to prove.” Id. “[T]he

reasoning or methodology underlying the testimony must not only be scientifically valid, it

also must be properly applied to the facts in issue.” Id. (alterations, emphasis, internal

quotation marks, and citations omitted).

{37} The district court found that in order for Dr. Dahlgren to apply his reasoning or

methodology reliably to the facts in the present case, Dr. Dahlgren’s opinion must be based

on some quantification of the dose of monensin received by the Parkhills. We agree.

“Expert testimony may be received if, and only if, the expert possesses such facts as would

enable him to express a reasonably accurate conclusion as distinguished from mere

conjecture.” Id. ¶ 32 (internal quotation marks and citation omitted). 

{38} While Dr. Dahlgren agreed that the dosage received by the Parkhills was critical in

determining whether exposure to monensin could have caused the Parkhills’ physical

symptoms, Dr. Dahlgren did not attempt to quantify the dose of monensin received by the

Parkhills, nor did he make any statement to the effect that it was not possible to quantify the

dose of monensin to which the Parkhills had been exposed. As our Supreme Court noted in

Downey, “[e]xperts may, and often do, base their opinions upon factual assumptions.” Id.

¶ 34. However, the court went on to state that “those assumptions in turn must find

evidentiary foundation in the record.” Id.

{39} We recognize that the precise dose of monensin received by the Parkhills may have

been difficult to assess; nevertheless, it appears from the testimony of ACMG’s expert, Dr.

Fisher, a board certified toxicologist, that it was possible under the circumstances in the

present case to give a reasonable estimate of the magnitude or concentration of monensin

exposure received by the Parkhills. 

{40} Dr. Dahlgren theorizes that the Parkhills’ exposure to monensin occurred primarily

through their inhalation of the dust from the feed generated during the feeding process.

Samples of the Parkhills’ feed, from the same lot as the feed that had been fed to the horses,
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were tested for monensin content by the New Mexico Department of Agriculture. Amounts

of monensin found in the feed ranged from less than 2.3 grams per ton up to 8 grams per ton.

Dr. Dahlgren, however, did not quantify any dosage based on these or any other tests.

{41} Dr. Fisher, on the other hand, made a determination of the likely worst-case dose of

monensin the Parkhills could have received by assuming the highest amount of monensin

found in any feed sample was present in all of the feed with which the Parkhills had contact.

He also assumed that an extremely dusty environment in which 1% of the air would be dust

from the grain (an environment in which it would be difficult to see more than a few feet)

was present all times during all feedings; that the Parkhills were in this environment for an

hour at each feeding; that the Parkhills inhaled the same volume of air that an average person

would have inhaled during that time; that all grain and monensin dust in the air was of a size

that could be inhaled and retained in the lungs; and that 100% of the amount inhaled was

absorbed into the body. 

{42} Based on this worst-case analysis, Dr. Fisher estimated that the maximum dose of

monensin the Parkhills could have received in each one hour exposure would have been

0.038 milligrams per kilogram of body weight, an amount that, in his opinion, was unlikely

to have caused any symptoms of toxicity in the Parkhills. 

{43} The Parkhills do not offer evidence or argument to rebut Dr. Fisher’s measurements

or analysis, but rather assert that because of the alleged temporal relationship between the

onset of the Parkhills symptoms and their exposure to monensin, quantifying the dosage

received is not necessary to render a scientifically reliable opinion as to the effect of the

exposure on the Parkhills. In support of their contention, the Parkhills cite several cases

from other jurisdictions for the proposition that temporal relationships may be useful in

determining causation where direct evidence of dosage cannot be obtained. Curtis v. M &

S Petroleum, Inc., 174 F.3d 661, 671 (5th Cir. 1999) (stating that the fact that workers

displayed well-known symptoms of benzene exposure shortly after exposure to an unknown

level of benzene could be used as a factor in determining dosage); Christian v. Gray, 2003

OK 10, ¶ 38, 65 P.3d 591 (stating that “the testimony of the expert should reveal a reliable

method for determining the quantity of the toxin necessary to cause injuries of the type

experienced by [the] plaintiff (general causation), unless [the] plaintiff can show that the

circumstances are such that general causation should not be necessary”); Wisner v. Ill. Cent.

Gulf R.R., 537 So. 2d 740, 748 (La. Ct. App. 1988) (stating that “where there are no facts,

such as the exact degree of [plaintiff’s] exposure, we hold the experts are still entitled to

offer their conclusions based on their areas of expertise”). These cases are not applicable

to the circumstances before us because direct evidence of the Parkhills’ monensin dosage

could have been obtained.

{44} The district court also found Dr. Dahlgren’s opinion to be unreliable based on his

“utter lack of familiarity” with monensin and the manner in which it is used and handled in

the industry. Dr. Dahlgren stated that prior to being hired for the purposes of this lawsuit,

he had no experience with or knowledge of monensin or any other chemical within the class

of antibiotics of which monensin is a part. Dr. Dahlgren stated that he was aware from the

reports and testimony of the other experts that monensin has been routinely used for many
12

years as an additive in cattle and chicken feed in concentrations up to fifty times greater than

the concentrations contained in the horse feed in the present case; however, Dr. Dahlgren

stated that he had not researched what protective equipment, if any, was used within the

industry when dealing with these feeds or whether there had been a single incident of health

problems with workers in the industry. Dr. Dahlgren was also unaware that other people

who had fed the monensin-contaminated feed (those feeding at the Dexter locations) had not

experienced any adverse health symptoms. In short, Dr. Dahlgren failed to lay a scientific

groundwork for the general toxicity of monensin and that it can cause the harm the Parkhills

suffered. 

{45} Finally, the district court noted that Dr. Dahlgren’s opinions were generated solely

for the purposes of the Parkhills’ litigation and that “[i]t did not appear from the evidence

that he had any specialized education in toxicology.” See Daubert v. Merrell Dow Pharms.,

Inc., 43 F.3d 1311, 1317 (9th Cir. 1995) (emphasizing that “[o]ne very significant fact to be

considered is whether the experts are proposing to testify about matters growing naturally

and directly out of research they have conducted independent of the litigation, or whether

they have developed their opinions expressly for purposes of testifying”).

{46} We reiterate the direction given by our Supreme Court that the trial court has broad

discretion in the admission or exclusion of expert evidence, and that the trial court’s decision

should be sustained “unless [it is] manifestly erroneous.” Alberico, 116 N.M. at 169, 861

P.2d at 205 (internal quotation marks and citation omitted). Applying this standard to the

facts of this case and based on a review of the record before us, we conclude that the district

court did not abuse its discretion when it excluded the testimony of Dr. Dahlgren as

unreliable. Therefore, we affirm the district court’s decision.

CONCLUSION

{47} For the reasons set forth above, we affirm the district court’s orders as to the

exclusion of Dr. Koury’s and Dr. Dahlgren’s causation testimony. In light of our conclusion

that the experts were properly excluded, we do not reach Mr. Parkhill’s claim that the district

court erred in dismissing his personal injury claims as a sanction for discovery abuse.

{48} IT IS SO ORDERED.

____________________________________

LINDA M. VANZI, Judge

I CONCUR:

____________________________________

JAMES J. WECHSLER, Judge
13

VIGIL, Judge (specially concurring).

{49} I agree with the majority that the district court did not abuse its discretion in

excluding the proposed expert testimony of Dr. Koury and Dr. Dahlgren. However, I follow

a fundamentally different analytical approach in considering the admissibility of this

proposed expert testimony. 

{50} The Daubert-Alberico factors are considered in relation to whether the methodology

used by an expert to arrive at a conclusion is scientifically valid. Daubert, 509 U.S. at 592-

93 (stating that a proffer of scientific testimony entails a “preliminary assessment of whether

the reasoning or methodology underlying the testimony is scientifically valid and of whether

that reasoning or methodology properly can be applied to the facts in issue”); Downey, 2008-

NMSC-061, ¶ 30 (stating that for scientific evidence to be admissible under Rule 11-702,

the reasoning or methodology underlying the testimony must be scientifically valid).

However, in its consideration of whether the doctors were qualified to testify, the majority

undertakes consideration of the Daubert-Alberico factors. Majority Op. ¶¶ 20-24, 32-35.

This is not only unnecessary, it causes confusion. 

{51} The Daubert-Alberico factors are considered only after the trial court has first

determined that the proposed expert is qualified and that the proposed testimony will be

helpful in deciding an issue of fact in the case. Neither of these two preliminary questions

requires an analysis of the Daubert-Alberico factors. The trial court then determines if the

proposed testimony involves scientific evidence. If the proposed testimony involves

scientific evidence, the trial court then considers the Daubert-Alberico factors to determine

if the methodology utilized by the expert is scientifically valid. If the proposed testimony

does not involve scientific evidence, the Daubert-Alberico factors are not applicable.

{52} My second major disagreement with the majority is its analysis of whether a

differential diagnosis performed by a qualified doctor may constitute sufficient proof of

causation in a toxic tort case. Courts disagree on whether a doctor relying on a clinical

differential diagnosis “can provide adequate proof of causation in a toxic tort action.”

Hollander v. Sandoz Pharms. Corp., 289 F.3d 1193, 1210 (10th Cir. 2002) (quoting Federal

Judicial Center, Reference Manual on Scientific Evidence, Supreme Court’s Trilogy on the

Admissibility of Expert Testimony, 34 (2d ed. 2000)). The result of the majority opinion

discussion of this issue at ¶¶ 20-24 and its reliance on McClain is to exclude a doctor from

ever being able to use a differential diagnosis to establish causation in a toxic tort case. Not

only do I disagree with such a sweeping conclusion, it is unnecessary. The admissibility of

evidence is specific to each case, and we should only determine whether the district court

abused its discretion in excluding the diagnoses in this case. See Hollander, 289 F.3d at

1210.

DISCUSSION

New Mexico Law Regarding the Admission of Expert Testimony
14

{53} The admission of all expert testimony is governed by Rule 11-702. Rule 11-702 is

entitled, “Testimony by experts,” and it provides:

If scientific, technical or other specialized knowledge will assist the

trier of fact to understand the evidence or to determine a fact in issue, a

witness qualified as an expert by knowledge, skill, experience, training or

education may testify thereto in the form of an opinion or otherwise.

{54} It is now settled that under Rule 11-702 there are three prerequisites for the

admission of all expert opinion testimony: “(1) experts must be qualified; (2) their testimony

must assist the trier of fact; and (3) their testimony must be limited to the area of scientific,

technical, or other specialized knowledge in which they are qualified.” Torres, 1999-

NMSC-010, ¶ 23. The burden is on the proponent of the testimony to satisfy each of the

prerequisites before the expert evidence is admissible. State v. Downey, 2008-NMSC-061,

¶ 25 (stating that Rule 11-702 predicates the admissibility of expert testimony on the

satisfaction of the three requirements); State v. Morales, 2002-NMCA-052, ¶ 21, 132 N.M.

146, 45 P.3d 406 (stating that expert testimony may be admitted under Rule 11-702 if the

proponent establishes these three prerequisites). I now discuss these prerequisites.

{55} First, “Regardless of whether the subject matter involves scientific, technical, or

other specialized knowledge, however, a witness must qualify as an expert in the field for

which his or her testimony is offered before such testimony is admissible.” Torres, 1999-

NMSC-010, ¶ 45; see Downey, 2008-NMSC-061, ¶ 26 (quoting Torres, 1999-NMSC-010,

¶ 45). The trial court’s determination is reviewed for an abuse of discretion. See Torres,

1999-NMSC-010, ¶ 40 (concluding that the evidence failed to establish that a police officer

was qualified to testify about the scientific bases of horizontal gaze nystagmus (HGN)

testing); State v. Stills, 1998-NMSC-009, ¶ 34, 125 N.M. 66, 957 P.2d 51 (examining the

evidence and concluding it supported a finding that the witness was an expert); State v.

Lasworth, 2002-NMCA-029, ¶ 17, 131 N.M. 739, 42 P.3d 844 (noting that the state

contended the trial court abused its discretion by ruling its witness was not qualified as an

expert). 

{56} If the witness is qualified, the second condition for the admission of expert evidence

must be satisfied. This requirement, that the testimony must assist the trier of fact, is

primarily one of relevance. Anderson, 118 N.M. at 291, 881 P.2d at 36. “One aspect of

relevance is whether expert testimony proffered in the case is sufficiently tied to the facts

of the case that it will aid the jury in resolving a factual dispute.” Downey, 2008-NMSC061, ¶ 30 (internal quotation marks and citation omitted). In addition, if the witness cannot

explain how the testimony proves an issue in the case, it does not assist the trier of fact. See

Torres, 1999-NMSC-010, ¶ 40 (concluding that since the testimony of a police officer did

not explain how a horizontal gaze nystagmus (HGN) test proved intoxication, his testimony

concerning the test did not assist the trier of fact); Rule 11-401 (defining “relevant evidence”

as “evidence having any tendency to make the existence of any fact that is of consequence
15

to the determination of the action more probable or less probable than it would be without

the evidence”).

{57} The third requirement for the admission of expert testimony has received the most

attention. In Alberico, 116 N.M. at 165-68, 861 P.2d at 201-04, our Supreme Court

abandoned the “general acceptance” test of Frye v. United States, 293 F. 1013, 1014 (D.C.

Cir. 1923), in favor of the more flexible Daubert test for determining if expert opinion

evidence involving “scientific knowledge” is reliable and therefore admissible under Rule

11-702. See also State v. Tollardo, 2003-NMCA-122, ¶ 17, 134 N.M. 430, 77 P.3d 1023

(stating that Alberico adopted “a more flexible inquiry” in which the general acceptance of

the theory or technique is considered but is not controlling). In determining whether to

admit expert opinion involving “scientific knowledge,” the trial court considers a nonexclusive list of factors adopted from Daubert which include: 

(1) whether a theory or technique can be (and has been) tested; (2) whether

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

the known potential rate of error in using a particular scientific technique and

the existence and maintenance of standards controlling the technique’s

operation; and (4) whether the theory or technique has been generally

accepted in the particular scientific field. 

Anderson, 118 N.M. at 291, 881 P.2d at 36 (internal quotation marks and citation omitted).

In Alberico, 116 N.M. at 167, 861 P.2d at 203, our Supreme Court added another factor: (5)

“whether the scientific technique is based upon well-recognized scientific principle and

whether it is capable of supporting opinions based upon reasonable probability rather than

conjecture.” See Anderson, 118 N.M. at 291, 881 P.2d at 36 (noting the addition of this

requirement by Alberico). The trial court’s application of the Daubert-Alberico factors is

reviewed for abuse of discretion. Tollardo, 2003-NMCA-122, ¶ 16. 

{58} However, the Daubert-Alberico factors apply only when the trial court is evaluating

scientific testimony; they do not apply when evaluating non-scientific testimony. Torres,

1999-NMSC-010, ¶ 43; State v. Aleman, 2008-NMCA-137, ¶ 6, 145 N.M. 79, 194 P.3d 110.

The initial question of whether the expert opinion involves scientific knowledge, which must

meet the standard of evidentiary reliability set forth in Daubert-Alberico presents a question

of law which is reviewed de novo. Torres, 1999-NMSC-010, ¶ 28; Aleman, 2008-NMCA137, ¶ 6; Tollardo, 2003-NMCA-122, ¶ 9; Morales, 2002-NMCA-052, ¶ 18.

{59} Summarizing: (1) The proponent of any expert evidence must first establish that the

proposed witness is qualified to give an expert opinion in the relevant field. This

determination lies in the discretion of the trial court. If the witness is not qualified, the

inquiry ends, and the evidence is not admissible. (2) If the witness is qualified as an expert,

the proponent of the evidence must demonstrate that the testimony will assist the trier of fact.

Again, this determination lies in the discretion of the trial court, and its determination will

depend on a myriad of factors, including the nature of the case, and the purpose for which
16

the evidence is being offered. (3) If the first two requirements are satisfied, the trial court

must then determine whether the proposed testimony involves scientific evidence. This is

an issue of law, reviewed de novo on appeal. The trial court applies the Daubert-Alberico

factors to assess whether the proposed testimony is reliable and therefore admissible if it

determines that the testimony involves scientific evidence. The Daubert-Alberico factors

do not apply if the expert testimony is non-scientific and is based on the knowledge,

experience, or training of the witness. To some degree, these considerations and the showing

required to satisfy them may overlap. However, to the extent possible, consideration should

be given to each separate prerequisite on its own. This will simplify and focus any pretrial

hearing which may be held to consider the admissibility of expert testimony and appellate

review of the trial court’s decision. 

{60} When all the factors are considered, the admission of expert testimony is within the

discretion of the trial court and will not be reversed absent a showing of abuse of that

discretion. Alberico, 116 N.M. at 169, 861 P.2d at 205. “An abuse of discretion standard

of review, however, is not tantamount to rubber-stamping the trial judge’s decision. It

should not prevent an appellate court from conducting a meaningful analysis of the

admission [of] scientific testimony to ensure that the trial judge’s decision was in accordance

with the Rules of Evidence and the evidence in the case.” Id. at 170, 861 P.2d at 206; see

Downey, 2008-NMSC-061, ¶ 24 (repeating this observation of Alberico). Moreover, in light

of the liberal approach of our rules of evidence to the admission of evidence and the

heightened qualifications of modern day jurors, any doubt regarding the admissibility of

expert opinion evidence “should be resolved in favor of admission, rather than exclusion.”

Lee v. Martinez, 2004-NMSC-027, ¶ 16, 136 N.M. 166, 96 P.3d 291 (citing 1 Jack B.

Weinstein & Margaret A. Berger, Weinstein’s Federal Evidence xix (2d ed. 2003)); see

Aleman, 2008-NMCA-137, ¶ 30. 

{61} I now apply the foregoing analysis to consider whether the district court abused its

discretion in this case when it ruled that the testimony of the Parkhills’ experts was not

admissible.

Qualifications of the Experts

{62} The foundation for determining whether the expert is qualified is to identify what the

issue is that requires expert testimony. This insures that an accurate determination can then

be made by the trial court that the witness has the requisite knowledge, skill, experience,

training, or education to qualify as an expert in the relevant field. 

{63} The central issue in this case is whether the monensin in the horse feed caused the

Parkhills’ adverse physical symptoms. On the record before the district court, it was

demonstrated that the most relevant field of expertise which applies in resolving this

disputed fact is toxicology. “The science of toxicology attempts to determine at what doses

foreign agents [monensin in horse feed] produce their effects [of adverse physical symptoms

in the Parkhills].” Federal Judicial Center, Reference Manual on Scientific Evidence,
17

Reference Guide on Toxicology, 403 (2d ed. 2000). Stated in legal terms, this is a classic

toxic tort case. “Scientific knowledge of the harmful level of exposure to a chemical, plus

knowledge that the plaintiff was exposed to such quantities, are minimal facts necessary to

sustain the plaintiffs’ burden in a toxic tort case.” Allen v. Pa. Eng’g Corp., 102 F.3d 194,

199 (5th Cir. 1996). 

{64} The Parkhills sought to introduce the opinion of Dr. Koury, their treating physician,

that the monensin in the horse feed caused their physical symptoms. The district court made

findings of fact that Dr. Koury is a family practice doctor who provided the services of a

family practitioner to the Parkhills, which included a diagnosis of their conditions and

treatment. On the other hand, the district court also found that Dr. Koury is not, and has

never been, trained as a toxicologist; he knew nothing about monensin prior to this litigation;

he did not estimate any dose of monensin to which the Parkhills were exposed; and he did

not estimate the duration of the Parkhills’ claimed exposure to monensin.

{65} The district court concluded that “Dr. Koury lacks the background, training and

experience required to render a reliable opinion on the subject whether monensin was the

external cause or etiology of the [Parkhills’] medical symptoms.” These findings are not

challenged, and they are supported by the evidence presented to the district court. I therefore

conclude that the district court did not abuse its discretion in determining that Dr. Koury was

not qualified under Rule 11-702. 

{66} The Parkhills also sought to introduce testimony from Dr. Dahlgren, whom they hired

to testify as an expert on causation. Dr. Dahlgren is board-certified in internal medicine, and

the Parkhills asserted his medical specialty is “assessing and diagnosing toxic exposures in

the environment[.]” However, Dr. Dahlgren had no idea how much monensin the Parkhills

were exposed to, and he made no attempt to calculate the dose. Moreover, Dr. Dahlgren

never heard of monensin before this case; knew nothing about livestock feeding practices

or the widespread use of monensin in livestock feed; had never studied the class of

antibiotics (ionophores) involved in this dispute before he was hired in this lawsuit; never

met, spoke to, or examined the Parkhills; and acknowledged he developed his opinions

regarding toxicity solely for purposes of this litigation.

{67} The district court found that it did not appear from the evidence that Dr. Dahlgren

had any specialized education in toxicology, that “his qualifications are less than stellar,”

and concluded that he was not qualified to testify as an expert. In light of the evidence

presented to the district court, I cannot conclude that the district court abused its discretion

in finding that Dr. Dahlgren was not qualified to render an opinion on causation in this case.

Expert Testimony Must Assist the Trier of Fact

{68} The Parkhills nevertheless argue that Dr. Koury and Dr. Dahlgren are medical

doctors who are qualified to perform a differential diagnosis. Since the opinions of the

doctors are based on the differential diagnosis they performed, the Parkhills assert that they
18

were qualified to testify that monensin in the horse feed caused their adverse physical

symptoms. I assume that a doctor’s experience or training qualifies the doctor to perform

a differential diagnosis and therefore proceed to an analysis of whether the Parkhills satisfied

the second requirement for the admission of expert testimony under Rule 11-702.

{69} A “[d]ifferential diagnosis refers to the process by which a physician rules in all

scientifically plausible causes of the plaintiff’s injury. The physician then rules out the least

plausible causes of injury until the most likely cause remains. The remaining cause is the

expert’s conclusion.” Hollander, 289 F.3d at 1209 (emphasis added) (alterations omitted)

(internal quotation marks and citation omitted); see Federal Judicial Center, Reference

Manual on Scientific Evidence, Reference Guide on Medical Testimony, 481 (2d ed. 2000)

(defining a differential diagnosis as “[t]he term used by physicians to refer to the process of

determining which of two or more diseases with similar symptoms and signs the patient is

suffering from, by means of comparing the various competing diagnostic hypotheses with

the clinical findings”). 

{70} To establish cause in a toxic tort case with a differential diagnosis, the evidence must

show both “general causation” and “specific causation.” See Norris v. Baxter Healthcare

Corp., 397 F.3d 878, 881 (10th Cir. 2005) (citing Raynor v. Merrell Pharms., Inc., 104 F.3d

1371, 1376 (D.C. Cir. 1997) (discussing causation in toxic tort cases in terms of general

causation and specific causation)). “General causation is whether a substance is capable of

causing a particular injury or condition in the general population and specific causation is

whether a substance caused a particular individual’s injury.” Id. at 881; see also Federal

Judicial Center, Reference Manual on Scientific Evidence, Reference Guide on Medical

Testimony, 481, 483 (stating that “[g]eneral causation is established by demonstrating

(usually by reference to a scientific publication) that exposure to the substance in question

causes (or is capable of causing) disease” and that “[s]pecific, or individual, causation is

established by demonstrating that a given exposure is the cause of an individual’s disease”).

A differential diagnosis to establish causation in a toxic tort case therefore necessarily

assumes that the “final, suspected cause remaining after the process of elimination must

actually be capable of causing the injury” or disease. See Norris, 397 F.3d at 885 (emphasis

omitted) (quoting Hall v. Baxter Healthcare Corp., 947 F. Supp. 1387, 1413 (D. Or. 1966))

(quoting Cavallo v. Star Enter., 892 F. Supp. 756, 771 (E.D. Va. 1995)), aff’d on this

ground, rev’d on other grounds, 100 F.3d 1150 (4th Cir. 1996). Thus, where the evidence

fails to establish that the suspected cause is actually capable of causing the injury or disease

(general causation), a differential diagnosis cannot reliably point to the suspected cause as

the actual cause (specific causation). In the language of Rule 11-702, this results in an

unreliable opinion that does not assist the trier of fact, and it is not admissible. See Downey,

2008-NMSC-061, ¶¶ 30, 32 (reiterating that expert testimony is inadmissible under Rule 11-

702 unless it will assist the trier of fact, and that expert testimony which is “mere conjecture”

is inadmissible (internal quotation marks and citation omitted)).

{71} I now turn to the specific facts of this case. The district court made specific findings

that Dr. Koury did not perform adequate research to reliably determine that monensin
19

generally is, to a reasonable medical probability, capable of causing the varied symptoms

observed in the Parkhills in the human population as a whole. “No such research has been

presented to the Court.” Instead, the district court found that Dr. Koury presumed general

causation, and “Dr. Koury has no reliable scientific basis for that presumption.” These

findings have support in the evidence presented to the district court and are not specifically

challenged.

{72} Dr. Dahlgren testified he was aware from the reports and testimony of other experts

that monensin has been routinely used for many years as an additive in cattle and chicken

feed in concentrations up to fifty times greater than the concentrations contained in the horse

feed in the present case; however, Dr. Dahlgren stated that he had not researched what

protective equipment, if any, was used within the industry when dealing with these feeds or

whether there had been a single incident of health problems with workers in the industry.

Dr. Dahlgren was also unaware that other people who had fed the monensin-contaminated

feed (those feeding at the Dexter locations) had not experienced any adverse health

symptoms. In addition, the district court was presented with evidence that the Parkhills’ own

veterinary toxicologist stated that in his nearly fifty years of experience as a veterinary

toxicologist, and despite monensin’s wide-spread use for more than thirty years in livestock

feeding operations throughout the world, “I’ve never known a human that’s been affected.”

{73} In light of the foregoing evidence, I conclude it was well within the discretion of the

district court to conclude that the differential diagnoses of Drs. Koury and Dahlgren were

not sufficiently reliable because they were lacking in the necessary foundation of general

causation. See Hollander, 289 F.3d at 1210-11 (concluding that differential diagnosis expert

testimony of a causal connection between a prescription drug (Parlodel) and the plaintiff’s

stroke was inadmissible because the trial court did not abuse its discretion in concluding the

experts failed to demonstrate by reliable evidence that the drug can cause strokes); Norris,

397 F.3d at 885-86 (holding that experts’ differential diagnoses that were contrary to all

available epidemiological evidence that silicone breast implants did not cause diseases at

issue were not admissible); Raynor, 104 F.3d at 1375-76 (holding that differential diagnosis

which concluded that Bendectine caused the child’s birth defects was inadmissible because

a link between Bendectine and birth defects (general causation) was missing). 

{74} In contrast to the case before us, in Ambrosini v. Labarraque, 101 F.3d 129, 135-36

(D.C. Cir. 1996), the court held that a differential diagnosis opinion was admissible to defeat

summary judgment in a case where the plaintiffs alleged that the prescription drug DepoProvera caused a child’s birth defects. The plaintiffs presented expert testimony from an

epidemiologist that the drug could cause birth defects like the child’s (general causation) and

testimony from an expert on birth defects that the drug caused the child’s birth defects

(specific causation). The court concluded that in light of this evidence, the experts’

testimony would assist the trier of fact to understand the evidence or determine a fact in

issue. Id. In the case before us, however, the differential diagnoses of Drs. Koury and

Dahlgren lack reliability and, therefore, would not assist the trier of fact. The consequence

is that their opinions are inadmissible. 
20

{75} The Parkhills argue this case presents “unique circumstances” and therefore general

causation is not required. I agree that the evidence may demonstrate to the trial court that

there are unique circumstances that make a presentation of evidence of general causation

unnecessary or impossible. See Hollander, 289 F.3d at 1211-12 (stating that a medical

expert must not always cite published studies on general causation in order to reliably

conclude that a particular object caused a particular illness where the first several victims

of a new toxic tort are involved “simply because the medical literature, which will eventually

show the connection between the victims’ condition and the toxic substance, has not yet been

completed”) (quoting Turner v. Iowa Fire Equip. Co., 229 F.3d 1202, 1209 (8th Cir. 2000));

Heller v. Shaw Indus., Inc., 167 F.3d 146, 155 (3d Cir. 1999) (stating that a medical expert

is not always required to cite published studies on general causation because this “would

doom from the outset all cases in which the state of research on the specific ailment or on

the alleged causal agent was in its early stages”; but emphasizing that the diagnosis must

otherwise be trustworthy); Ambrosini, 101 F.3d at 138 (stating “the fact that a case may be

the first of its type, or that the plaintiff’s doctors may have been the first alert enough to

recognize a causal connection,” does not render an expert’s opinion inadmissible and that

when an expert is “concededly well qualified” in the field and “when the underlying basis

or methods of an expert’s opinions are of a type reasonably relied upon by the experts in the

field, the court must allow the opinion to be assessed by the factfinder” (alteration omitted)

(internal quotation marks and citations omitted). In addition, I note Rubanick v. Witco

Chem. Corp., 593 A.2d 733, 747-48 (N.J. 1991), in which the New Jersey Supreme Court

undertook a general analysis of cases addressing causation in toxic tort cases and concluded:

[W]e hold that in toxic-tort litigation, a scientific theory of causation that has

not yet reached general acceptance may be found to be sufficiently reliable

if it is based on a sound, adequately-founded scientific methodology

involving data and information of the type reasonably relied on by experts in

the scientific field. The evidence of such scientific knowledge must be

proffered by an expert who is sufficiently qualified by education, knowledge,

training, and experience in the specific field of science. The expert must

possess a demonstrated professional capability to assess the scientific

significance of the underlying data and information, to apply the scientific

methodology, and to explain the bases for the opinion reached.

However, I agree with Defendant that the Parkhills failed to demonstrate to the district court

that such unique circumstances exist in this case to conclude that the district court abused

its discretion in excluding the opinions of Drs. Koury and Dahlgren.

CONCLUSION

{76} For the foregoing reasons, I agree with the majority that the district court did not

abuse its discretion by excluding Plaintiff’s proffered expert testimony in this case. I also

agree with the majority that Banks does not apply in considering the admissibility of the

Parkhills’ expert testimony. Majority Op. ¶ 23. However, because the majority undertakes
21

a fundamentally different analysis in considering the admissibility of the proposed expert

testimony, and the majority analysis goes too far by excluding differential diagnosis

testimony to establish cause in all toxic tort cases, I specially concur. 

_____________________________________

MICHAEL E. VIGIL, Judge

Topic Index for Parkhill v. Alderman-Cave Milling, Docket No. 29,120

AE APPEAL AND ERROR

AE-SR Standard of Review 

CP CIVIL PROCEDURE

CP-EH Evidentiary Hearing

CP-EX Expert Witnesses

EV EVIDENCE

EV-EW Expert Witness

EV-SC Scientific Evidence & Daubert Standard

TR TORTS

TR-TX Toxic Tort