The plaintiff, Baker Valley Lumber, Inc. (Baker Valley), appeals a ruling by the Superior Court {Sullivan, J.) barring the testimony of its expert witnesses under New Hampshire Rule of Evidence 702 and dismissing its negligence and products liability claims against defendants Ingersoll-Rand Company (Ingersoll-Rand) and Air Services of NH, Inc. (Air Services). We reverse the dismissals and remand to the trial court.
On March 25, 1995, a fire destroyed the Baker Valley sawmill in Rumney. Employee witnesses and the fire marshal’s investigation identified the room housing the mill’s air compressor as the source of the fire. On January 9, 1998, Baker Valley commenced litigation against Ingersoll-Rand, the manufacturer of the compressor, and Air Services, which serviced and maintained the compressor.
To prove its claims at trial, Baker Valley planned to introduce testimony from two experts: Richard W. Jones, a fire investigator, and Dr. Igor Paul, an adjunct professor of mechanical engineering at the Massachusetts Institute of Technology (MIT). Both experts concluded that a defect in the compressor’s hose or fitting allowed highly-pressured oil to escape from the compressor. They believed that a spark then ignited this oil, causing the fire. Jones reached this conclusion by studying the charred air compressor, the fire marshal’s report and the relevant depositions, and by conducting an experiment. By eliminating other possible causes, he concluded that the defect in the air compressor caused the fire. Dr. Paul’s methodology involved studying the timing of the fire, the behavior of hydraulic vapor in the compressor, the color of the fire’s smoke, and the appearance of the fire. Dr. Paul arrived at his conclusion largely by eliminating other possible causes.
The defendants challenged the admission of this testimony under New Hampshire Rule of Evidence 702. At the defendants’ request, the trial court conducted a three-day hearing to determine whether the plaintiffs expert testimony was sufficiently reliable to be admissible. During this hearing, the defendants called their own expert, Dr. John Wilson, who testified, inter alia, that the temperature in the compressor room was too cold for the oil to become pressurized as the plaintiffs experts theorized. In response, the plaintiff called Jones to testify. Jones reiterated his theory and submitted to an extensive voir dire from the defendants’ lawyers. The plaintiff also introduced the deposition of Dr. Paul.
On the second day of the hearing, the trial court ruled that Jones was not qualified to testify as an expert about his theory of the fire’s causation. Several months later, the trial court issued an extensive opinion barring
After we accepted this appeal, we authorized the trial court to decide two pending motions relating to Air Services. The trial court held that: (1) Dr. Paul could not, in any event, testify against Air Services because the plaintiff had not properly disclosed him to Air Services under Superior Court Rule 35(f); and (2) Jones was not qualified to testify about the service practices of Air Services.
On appeal, the plaintiff argues that the trial court erred in finding Jones unqualified as an expert, in ruling that the theory presented by the plaintiffs experts was unreliable, and in determining that it had not properly disclosed the witness under Rule 35®. The plaintiff has not briefed the trial court’s determination that Jones was not qualified to testify about the service practices of Air Services, and thus we decline to review this ruling. We address the remaining issues in turn.
We first consider whether the trial court erred in ruling that Jones is unqualified to testify as an expert concerning the plaintiffs pressurized oil theory. New Hampshire Rule of Evidence 702 states that an expert may be qualified on the basis of “knowledge, skill, experience, training, or education.” N.H. R. Ev. 702. We will reverse a trial court’s determination of expert qualification if we find it to be an unsustainable exercise of discretion. See State v. Santamaria,
The record establishes that Jones had over fifty years of experience investigating fires, and fifty years of experience working with compressors. Jones, in fact, testified that he had personally investigated “more than a dozen” cases involving air compressors, although he had never before concluded that an air compressor was the cause of a fire. Despite Jones’ extensive background, the trial court found him unqualified because he lacked personal experience with cases involving “a spray or mist turning into ... a gas and filling the atmosphere so it could float into an ignition source.”
The threshold for expert qualification, however, does not require the degree of specialization mandated by the trial court. “While the trial court may rule that a certain subject of inquiry requires that a member of a
The trial court also based its decision upon Jones’ lack of knowledge about the scientific processes in his theory and his unfamiliarity with the relevant scientific literature. Formal academic knowledge, however, is only one means by which an expert may be qualified to testify under Rule 702. In this case, Jones’ extensive expertise in “practical engineering,” acquired from his work in fire investigation and with compressors, was sufficient to qualify him based upon his “knowledge, skill, experience, training, or education.” N.H. R. Ev. 702.
Finally, the trial court noted that Jones did not conduct an experiment that successfully recreated his explanation of the fire’s cause. This fact is not relevant to his qualification as an expert, but instead relates to the weight and credibility of his testimony, which is to be evaluated by the fact-finder. See Emerson v. Bentwood,
The trial court ruled that the plaintiffs other expert witness, Dr. Paul, was qualified to testify about the plaintiffs theory concerning the cause of the fire. At oral argument, counsel for Air Services suggested that the trial court’s determination was incorrect. This issue, however, is not raised in either of the defendants’ briefs, and so we decline to address it.
Given that both Jones and Dr. Paul are qualified as experts, we next consider whether their testimony is admissible. Rule 702 states that a qualified expert may offer testimony if “scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue.” N.H. R. Ev. 702. Thus, expert testimony “must rise to a threshold level of reliability to be admissible.”
Although Daubert is binding only in federal court, the text of New Hampshire Rule of Evidence 702 is identical to the federal rule at the time of the Daubert decision. Compare Daubert,
The trial court concluded that Dr. Paul’s testimony was unreliable under both the Frye and Daubert standards. Because New Hampshire Rule of Evidence Rule 702 supersedes the Frye test, cf. Daubert,
The trial court relied upon a four-part test derived from State v. Cressey as a framework for its reliability analysis. This test considers: (1)
The trial court also found that Dr. Paul’s theory of fire causation was unreliable based upon several gaps in his testimony. At the hearing, the defendants’ expert, Dr. Wilson, testified that the low vapor pressure of the compressor oil, combined with the temperature of the compressor room, would tend to compress the oil rather than vaporize it. Dr. Paul did not specifically address these arguments in his prior deposition, nor did he explain how the compressor produced the spark that he believed caused the fire. Dr. Paul’s failure to address certain counter-arguments or to explain certain aspects of his theory, however, does not make his testimony per se unreliable. Rather, these omissions concern the relative weight and credibility of competing expert testimony rather than the basic reliability of such testimony, and are the province of the fact-finder, not the trial court. See Emerson,
To the extent that the trial court relied on the Daubert factors, it erred by focusing upon the reliability of the expert’s conclusion, rather than the reliability of the underlying technique used to reach that conclusion. See Daubert,
The proper focus for the trial court is the reliability of the expert’s methodology or technique. The trial court functions only as a gatekeeper, ensuring a methodology’s reliability before permitting the fact-finder to determine the weight and credibility to be afforded an expert’s testimony. Daubert,
In this case, Dr. Paul’s hypothesis about the origin of the fire was based largely upon his elimination of other possible causes. We agree with the plaintiff that this sort of methodology may be described as a “differential etiology.” Although courts have found differential etiology reliable in medical diagnoses, see, e.g., Westberry v. Gislaved Gummi AB,
We remand this question to the trial court. Specifically, the court must determine whether the differential etiology employed by Dr. Paul was reliable in this particular fire investigation. In determining reliability, the court may find the four factors outlined in Daubert to be helpful. These factors consider: (1) whether the results of the differential etiology used in this fire investigation are capable of being tested; (2) whether the use of such a differential etiology has been subjected to peer review and publication; (3) the error rate of fire investigation conclusions based upon this differential etiology, and (4) whether there is general acceptance in the scientific community of the use of such etiology in fire investigations. See Daubert,
We also remand the issue of the reliability of Richard Jones’ expert testimony. Jones stated in his affidavit that he “considered every possible
We emphasize that our adoption of Daubert does not require a trial court to conduct a pre-trial hearing in every case involving disputed expert testimony. The decision to hold such an evidentiary hearing rests within the trial court’s sound discretion. See, e.g., United States v. Charley,
Finally, we address the disclosure violation found by the trial court. The court determined that the plaintiff violated Superior Court Rule 35(f) by failing to disclose that Dr. Paul would be a witness against Air Services, and therefore ruled that Dr. Paul’s testimony could not be used against Air Services. We review a court’s exclusion of expert testimony for an unsustainable exercise of discretion. See Santamaria,
The relevant language of Superior Court Rule 35(f) requires a party to “state the subject matter on which the expert is expected to testify.” We have held that the “subject matter” of expert testimony includes “the substance of the facts and opinions” about which the expert is expected to testify. O’Donnell v. Moose Hill Orchards,
In this case, consistent with Superior Court Rule 35(f), the plaintiff filed a timely disclosure explaining that Dr. Paul “is expected to provide expert testimony with respect to the claim against Ingersoll-Rand,” and briefly describing Dr. Paul’s theory of the fire’s origin. Because this disclosure says nothing about testimony concerning inadequate servicing
The trial court also prohibited Dr. Paul from testifying against Air Services regarding the subject matter contained in the plaintiff’s disclosure. As best as we can determine, the argument advanced by Air Services is that the identity of the defendant against whom the witness will offer testimony is part of the “subject matter” of that testimony. Thus, Air Services contends that by failing to identify the defendant against whom the expert testimony will be used, a plaintiff forfeits the ability to use that expert against that defendant. We decline to adopt this reasoning under the circumstances of this case. First, because the theory of fire causation advanced by Dr. Paul is a necessary predicate to the claims against both Ingersoll-Rand and Air Services, the plaintiffs disclosure filed with the court was sufficient to put Air Services on notice that Dr. Paul’s testimony could be used against it. Second, Air Services was clearly not prejudiced by the plaintiff’s method of disclosure. Air Services’ counsel, in fact, appeared at Dr. Paul’s deposition subsequent to the disclosure and asked him a series of questions. We thus hold that the trial court’s exclusion of all his disclosed testimony against Air Services was an unsustainable exercise of discretion.
Reversed and remanded.