The opinion of the court was delivered by: Conboy, J.
The State appeals orders of the Superior Court (Wageling, J.) granting motions of the defendant, David McLeod, to preclude certain expert testimony and to suppress an audio-recording of a one-party telephonic interception, see RSA 570-A:6 (2001). We reverse in part, vacate in part, and remand.
I. Facts and Procedural History
The following facts are derived from the record. This heretofore "cold" case arises from a fire that occurred at an apartment building in Keene on January 14, 1989. The fire began in the second floor apartment of Sandra Walker. Walker and several other occupants of the building were unharmed by the fire; however, four members of a family living in the building died of smoke inhalation.
On the night before the fire, Ed Bussieres, who lived on the first floor, hosted a party, attended by both Walker and the defendant. Walker left the party between 7 p.m. and 9 p.m. to visit Linda Colburn, a friend who lived nearby. Walker returned from Colburn's apartment between 11 p.m. on January 13 and midnight, and went to her own apartment. Walker drank heavily during the night.
In the early morning hours of January 14, Walker awoke to find flames in her apartment. Over the course of several interviews with Keene police officers and Fire Investigator Thomas Norton, Walker gave differing accounts as to where she saw flames when she awoke, and how she believed the fire started.
When first interviewed by police, she stated that she assumed she fell asleep with a burning cigarette, and that she awoke to find her bed and the nearby wall completely engulfed in flames. She tried to put out the fire with her hands, but the flames intensified. She stated that she walked to the bathroom, where she filled a coffee pot with water. When she left the bathroom and looked at the bed, however, she "just saw flames." After realizing that she could not put out the fire, she ran out of her apartment. Based, in part, on the initial interviews with Walker, Norton reached the preliminary conclusion that the cause of the fire was "smoking materials."
Thereafter, the Keene Police Department reported that certain witnesses had implicated the defendant in starting the fire. One witness told officers that the defendant said, "How'd I do[?] [M]ake sure you go to the insurance company." Several other witnesses recounted hearing similar statements. Another witness stated that the defendant commented before the fire, "I'm going up to [Bussieres's] to get some coke and torch the place." The defendant denied involvement in the fire.
After receiving this information, Norton and the police again interviewed Walker. A police officer told her that the police suspected the defendant had started the fire. Walker stated that she did not know whether she had been smoking a cigarette but that she rarely smoked in the bedroom. She stated that she saw low flames around the couch, did not remember coughing, and that her eyes were burning a little bit, but not badly. She also said that she barely knew what was going on around her and that she was "very hazy."
Norton went back to the scene, and conducted a "controlled burn test." He applied a flame to a piece of stuffing from Walker's couch, which created so much smoke that he had to stop the experiment after six minutes. Norton ultimately concluded that the fire started on the couch and was the result of an "incendiary act" -- that is, that the introduction of an open flame to the couch caused it to ignite. He ruled out the possibility the fire was caused by "smoking materials."
The State then assembled a grand jury for the purpose of investigating the fire. Following the grand jury's investigation, the State did not pursue charges against the defendant.
In 2010, some twenty-one years later, the State's Cold Case Unit reinvestigated the fire. Prior to the initiation of the new investigation, Walker died and some of the evidence related to the fire was lost or destroyed, including the couch. The Cold Case Unit hired two experts from the United States Alcohol, Tobacco and Firearms Bureau (ATF): Special Agents Andrew Cox and John Pijaca. ATF is the primary federal agency that investigates fire incidents.
Because fire science had changed since 1989, Cox agreed to review and investigate Norton's conclusions. Cox determined that Norton's methodology and conclusions were consistent with the current scientific method outlined in the National Fire Protection Agency's Guide for Fire and Explosion Investigations (NFPA 921), which was developed after 1989. NFPA 921 is the definitive treatise to which fire investigators look in order to comply with the applicable scientific standards of reliability. Cox further concluded that the origin of the fire was the area of the bed and the couch, but could not narrow it to the couch only. He agreed that the fire was caused by a human incendiary act with an open flame, rather than a smoldering cigarette. Pijaca reviewed Cox's opinions and report, and agreed with his conclusions as to the origin and cause of the fire. In July 2010, the defendant was indicted on four counts of second degree murder, see RSA 630:1-b, I(b) (2007).
Before trial, the defendant moved to preclude the testimony of Norton, Cox, and Pijaca on the ground that their opinions are based upon Walker's hearsay statements. The defendant argued that Walker's statements were so "vague, ambiguous and inconsistent" as to be an unreliable basis for scientific analysis. The defendant also argued that the State's experts did not apply "accepted scientific methodology in formulating and testing their hypotheses."
Finally, the defendant asserted that the opinions were inadmissible pursuant to the Sixth and Fourteenth Amendments to the United States Constitution; Part I, Article 15 of the New Hampshire Constitution; RSA 516:29-a (2007); and New Hampshire Rules of Evidence 402, 403, 702, and 703. The State objected.
The State moved, in limine, to admit Walker's statements through the testimony of its experts. The defendant sought to preclude the introduction of Walker's statements, arguing that their introduction would violate his right to confront witnesses against him as guaranteed by the Federal and State Constitutions.
The trial court held evidentiary hearings at which Norton, Cox, and Pijaca testified and were subject to cross-examination. In relevant part, they testified that in arriving at their conclusions as to the cause and origin of the fire, they relied upon: witness statements; reported witness demeanor; physical evidence, such as burn patterns at the scene; field tests; fire studies; and their prior training and experience. They testified that NFPA 921 requires an investigator to consider witness statements at every step of the investigation, and that it provides that witness interviews are a necessary component of fire investigation. Norton testified that it is common practice in the field to rely upon witness statements.
The experts testified that they took into account Walker's statements and physical condition in ruling out a "smoldering fire" and concluding that the fire resulted from an open flame. According to Norton:
[I]f the fire were the result of smoking materials[,] it would be expected that Walker would have succ[u]mbed or suffered from smoke inhalation and burns. The reason for this is the advanced stage of burning, for a cigarette fire, she describes. Smoking materials fire starting in a couch stuffed with cotton fib[ers] takes over an hour to erupt into flames. During this time[,] large amounts of smoke and carbon monoxide are produced[,] which would cause injury or death.
Norton conceded on cross-examination that some of Walker's statements were inconsistent.
Following the evidentiary hearings, the trial court issued an order precluding admission of the State's experts' opinions and Walker's statements. The trial court did not rule that the experts improperly relied upon Walker's statements under the Rules of Evidence or NFPA 921. Instead, it concluded that "[b]ecause the experts' opinions were not independent from Walker's testimonial statements, allowing the experts to testify about the statements would violate the [d]efendant's [Confrontation Clause] rights." The trial court reasoned that without Walker's statements, the defendant could not engage in a threshold level of inquiry of the experts, and in order to "get to the heart" of the experts' statements' accuracy and reliability, the "[d]efendant [would] be placed in an untenable position of having to introduce ...