¶ 1. The State of Vermont appeals from the trial court’s dismissal of a civil driver’s license suspension complaint. The trial court found that the statutory requirements for civil suspension had not been met. We affirm.
¶ 2. The following facts are uncontested. On April 30, 2011, at 11:51 p.m., defendant was stopped in Newbury by Vermont State Trooper David Shaffer after ignoring a “Road Closed — High Water” sign and crossing a flooded roadway. Trooper Shaffer, smelling alcohol, asked defendant to perform a preliminary breath test and field sobriety tests. Based on the results of those preliminary tests, defendant was taken to thе Bradford Police Department, where Trooper Shaffer performed a series of breath tests with the station’s DataMaster DMT blood-alcohol-content-measurement device. 1
¶ 3. At 1:51 a.m., Trooper Shaffer obtained a reading of .101 from the first DMT test. Defendant requested a second test. At 1:52 а.m., the DMT device returned a reading of “standard out of range.” Trooper Shaffer attempted to perform a third test, but received a report of “invalid sample” at 1:59 a.m. On the fourth try, at 2:01 a.m., the DMT reported a blood-alcohol content of *468 .109. Defendant was informed of his right to obtain an indeрendent test.
¶ 4. Defendant was processed for driving while under the influence, and the State sought civil suspension of defendant’s license. On August 8, 2011, a final civil suspension hearing was held pursuant to 23 V.S.A. § 1205(h). At the hearing, defendant argued primarily that the statutory requirements for civil suspension had not been met. In particular, dеfendant raised the following issues: (1) whether valid and reliable testing methods were used and whether the results of the tests were accurate and accurately evaluated, and (2) whether the requirements of 23 V.S.A. § 1202 were satisfied. Most specifically, defendant contended that he did not receive the stаtutorily permitted second test under § 1202(d)(5), which allows a motorist who submits to an evidentiary breath test to “elect to have a second infrared test administered immediately after receiving the results of the first test.” Defendant argued that the second test was invalid because it was not taken in complianсe with the testing procedure adopted by the Vermont Criminal Justice Training Council and the Vermont Department of Health in the DataMaster DMT Addendum to its breath testing manual.
¶ 5. The manual, which dictates the proper operating procedures for DMT testing, specifies that DMT devices can expеrience fatal and nonfatal errors. Nonfatal errors are those that “may be remedied by the test operator,” and once “the error has been cleared,” the testing procedure can be resumed. When a fatal error occurs, however, the manual provides that the DMT shоuld be designated “out of service” and a detailed message should be left for the DMT supervisor. The manual states that a report of “standard out of range” is a fatal error. After receiving a fatal error, the manual instructs that the officer should “proceed to a different DataMaster,” and, “[i]f another DataMaster is not reasonably available, blood may be drawn.” The manual’s stated objective is for police officers to operate the DMT machine “in accordance with the specified procedure incorporated in this training.”
¶ 6. At the final merits hearing, the State presented testimony from its forensic chemist, Amanda Bolduc. Ms. Bolduc testified that she believed that the DMT device was “functioning properly at the time of the test[s]” and that there was no reason to doubt the reliability of the result obtained from the successive test effort *469 that yielded the .109 BAC. Although the manuаl indicates that a machine should be taken out of service following the receipt of a fatal error, such as a “standard out of range” reading, Ms. Bolduc opined that if an officer tries the device again and it gives a valid reading, “it’s fine.” She noted that the Department of Health’s manual uses the word “should” not “must” when describing the procedures to follow after obtaining a “standard out of range” reading. During cross-examination of Ms. Bolduc, defendant sought to cast doubt on the reliability of the majority of DMT machines and the validity of their test results, questioning Ms. Bolduc about her own expressed frustration with the devices, their malfunctions and glitches, and in particular, her dissatisfaction with one device that emitted plumes of smoke when turned on.
¶ 7. In a memorandum of law submitted after the final hearing, the State contended that Ms. Bolduc’s testimony established that the testing methods complied with the Department of Health’s rules. As a result, the State maintained, the testing methods and results were entitled to a presumption of validity, reliability, and accuracy.
¶ 8. The trial court dismissed the State’s contention that use of the term “should” in the Department of Health’s manual allowed the officer to exercise his own discretion with respect to the testing procedure. The court determined that the State did not comply with its own testing procedures and that this failure to adhere to the protocol deprived defendant of a valid and reliable second test as required by § 1202. Noting that the civil-suspension statute requires compliance with the testing statute, the trial court found the State had failed to adequately establish the elements necessary for the civil suspension and dismissed the complaint. The State appealed.
¶ 9. The State urges two primary grounds for reversal. First, the State argues that the officer’s failure to administer the second breath test in compliance with the State’s own training manuals is insufficient grounds to deem the second test unreliable, and thus inadmissible. The court cannot, the State maintains, “exclude” breath-test results based on the “mere possibility” of inaccuracy. Second, the State contends that the first breath test was reliable — notwithstanding the later nonfatal and fatal error messages — and was, in and of itself, sufficient to sustain a civil suspension of the defendant’s license. Neither argument is availing.
*470 ¶ 10. As a threshold matter, we note that the trial court predicated its dismissal of the civil-suspensiоn complaint not on the admission or exclusion of any breath-test evidence but rather on the State’s failure to comply with every element of the civil-suspension regime. The trial court found that the trooper’s departure from the Department of Health’s operating protocоl undermined the reliability of the later breath test effort that yielded a BAC result. That irregularity, the court reasoned, deprived defendant of a statutory right to a valid and reliable second test, negating an element necessary to sustain the State’s civil complaint.
¶ 11. The trial court’s determinations reрresent both findings of fact and conclusions of law, which we analyze according to their respective standards of review. Under the civil-suspension statute, a trial court is expressly authorized to consider the reliability of testing procedures and the accuracy of results. See § 1205(h)(1)(D) (final-heаring issues include “whether the testing methods used were valid and reliable, and whether the test results were accurate and accurately evaluated”). Whether a test is reliable or accurate is a factual finding. We review the trial court’s factual finding for clear error, “recognizing that the trier-оf-fact is in the best position to determine the weight and sufficiency of the evidence presented.”
State v. Santaw,
¶ 12. The trial court’s assessment of the tests’ reliability necessarily involved an assessment of the credibility of Ms. Bolduc’s testimony. Ms. Bolduc testified that if a fatal error occurs during an officer’s administration of a DMT breath test, the officer may try another test, and if the machine works during that test, “it’s fine.” This testimony contradicted the Department of Health’s manual, which provides that, in the event of a fatal error, the machine should be taken out of service, presumably because the machine did not opеrate properly. Because credibility determinations are solely within the province of the fact finder,
Omega Optical, Inc. v. Chroma Tech. Corp.,
¶ 13. It is true, as the State points out, that “[e]vidence that the test was takеn and evaluated in compliance with rules adopted by the department of health shall be prima facie evidence that the testing methods used were valid and reliable and that the test results are accurate and were accurately evaluated.” § 1205(h) (1)(D). 2 Here, however, the second successful test was definitively not conducted in compliance with the State’s own procedures. Where an officer does not comply with operating procedures, the fact finder is free to find the converse of that presumption.
¶ 14. On appeal, the State also argues that the validity of the second test’s results was immaterial becausе the first breath test was reliable and therefore sufficient on its own to sustain a civil suspension. The trial court found that a reliable second test was a necessary element of the civil-suspension procedure that the State failed to establish. We review such a conclusion of law de novo. See e.g.,
State v. Therrien,
¶ 15. Under Vermont law, a civil suspension is a summary proceeding designed to rapidly remove potentially dangerous drivers from public roadways.
State v. Anderson,
¶ 16. The State contends that the existence of a first, valid and reliable test is sufficient for сivil suspension. To accept, this assertion would render portions of both the testing statute and the civil-suspension review procedures meaningless. See 28 V.S.A. § 1205(h)(1)(E) (permitting final-hearing review of compliance with § 1202). “Generally, we do not construe a statute in a way that renders a significant part of it рure surplusage.”
In re Lunde,
¶ 17. On appeal, the State relies on a series of criminal drunk-driving cases dealing with the admissibility of blood-alcohol
*473
test results. This reliance is misplaced. Although the cases the State cites do relate to the validity and reliability of evidentiary breath tests, they do so in a different context not directly implicated in this case. The State puts partiсular emphasis, for example, on
State v. Vezina,
¶ 18. In sum, the trial court’s factual findings regarding the unreliability of the second test were not clearly erroneous, and the court correctly concluded that the lack of a reliable second test deprived the State of an essential element to establish its civil-suspension case.
Affirmed.
Notes
Trooper Shaffer took defendant to the Bradford Police Department, rather than the Bradford State Police Barracks, where Trooper Shaffer is based, because the DMT at thе state police barracks was out of order.
At the time this ease was initiated, the Department of Health was responsible for promulgating the rules governing use of the DMT devices. Section 1205(h)(1)(D) now provides that the Department of Public Safety is responsible for the rules’ adoption. See 2011, No. 56, § 16, effective March 1, 2012.